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Question 1 Report
Which of the following mixtures is an example of a colloid?
Answer Details
A colloid is a type of mixture where tiny particles of one substance are dispersed evenly throughout another substance. The particles in a colloid are larger than the molecules in a solution, which allows them to scatter light and give the mixture a cloudy or opaque appearance. Now let's analyze each option to determine which one is an example of a colloid:
1. Milk: Milk is an example of a colloid. It consists of tiny fat globules (particles) dispersed throughout a watery substance. When light shines through milk, it scatters off of the fat globules, giving it a cloudy appearance.
2. Orange juice: Orange juice is not an example of a colloid. It is a homogenous mixture of water and dissolved molecules, such as sugars and vitamins. The particles in orange juice are too small to scatter light.
3. Saltwater: Saltwater is a solution, not a colloid. It consists of salt (solute) dissolved in water (solvent). In a solution, the particles are very small and evenly distributed, and they do not scatter light.
4. Sugar dissolved in water: Sugar dissolved in water is also a solution, not a colloid. The sugar particles are molecular in size and are completely dispersed in the water.
In conclusion, milk is the only option that is an example of a colloid. The tiny fat globules in milk are larger than the molecules in a solution, causing them to scatter light and give the mixture its cloudy appearance.
Question 2 Report
What is the main environmental concern associated with sulfur dioxide emissions?
Answer Details
The main environmental concern associated with sulfur dioxide emissions is the formation of acid rain.
When sulfur dioxide (SO2) is released into the atmosphere, it reacts with oxygen and water vapor to form sulfuric acid (H2SO4). This acid then falls back to the Earth's surface as acid rain.
Acid rain can have damaging effects on the environment, including lakes, forests, and buildings. It can make water bodies more acidic, which harms aquatic plants and animals. It can also damage trees and vegetation, making it difficult for them to grow and survive. In addition, acid rain can corrode buildings, statues, and other structures made of stone or metal.
So, the main environmental concern associated with sulfur dioxide emissions is the formation of acid rain, which can have destructive impacts on ecosystems and man-made structures.
Question 3 Report
Which halogen is a gas at room temperature and is pale yellow in color?
Answer Details
Fluorine is a halogen that is a gas at room temperature and is pale yellow in color. Halogens are a group in the periodic table consisting of five chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Among these, only Fluorine and Chlorine are gases at room temperature, but Chlorine is greenish-yellow, not pale yellow.
Question 4 Report
The lanthanides and actinides are located in which block of the periodic table?
Answer Details
The lanthanides and actinides are located in the f-block of the periodic table.
The periodic table is organized into blocks based on the electron configuration of the elements. The f-block elements are located at the bottom of the periodic table, separated from the rest of the elements.
The lanthanides and actinides are a group of elements that have similar properties and electron configurations. They are also known as the "rare earth elements." These elements have electrons filling the 4f and 5f orbitals, hence they are placed in the f-block.
The f-block elements are very important in many scientific and technological applications. They are used in the production of magnets, catalysts, high-strength alloys, and various electronic devices. Some lanthanides and actinides are also used in medical imaging and cancer treatments.
Overall, the f-block elements play a crucial role in various fields of science and technology, and their placement in the periodic table helps to highlight their unique properties and characteristics.
Question 5 Report
Which separation technique is used to separate different pigments in a mixture based on their affinity for a stationary phase and a mobile phase?
Answer Details
The separation technique used to separate different pigments in a mixture based on their affinity for a stationary phase and a mobile phase is chromatography.
Chromatography is a method that takes advantage of the fact that different substances have different affinities for the components of the mixture. It involves two phases: the stationary phase and the mobile phase.
The stationary phase is a solid or a liquid that does not move, while the mobile phase is a liquid or a gas that moves through or over the stationary phase.
When the mixture is applied to the stationary phase, the pigments begin to separate based on their affinity for each phase. Some pigments may have a higher affinity for the stationary phase, causing them to move more slowly, while others have a higher affinity for the mobile phase, causing them to move more quickly.
As the mobile phase moves through the stationary phase, the individual pigments are carried along at different rates, resulting in their separation. The separated pigments can then be collected and analyzed.
In summary, chromatography is used to separate different pigments in a mixture based on their affinity for a stationary phase and a mobile phase. It exploits the fact that each pigment has a different affinity for the phases, allowing for their separation and analysis.
Question 6 Report
What is the state of matter in which particles are widely spaced and move freely with high kinetic energy?
Answer Details
The state of matter in which particles are widely spaced and move freely with high kinetic energy is gas.
Gas is one of the four fundamental states of matter, along with solid, liquid, and plasma. In the gas state, the particles are not tightly packed together like in solids and liquids. Instead, they are widely spread apart and move around in random directions at high speeds.
The high kinetic energy of gas particles allows them to move freely and independently from one another. They are not constrained by any definite shape or volume, which means gases can expand to fill the entire container they are placed in.
Particles in a gas state have weak attractive forces between them, resulting in the lack of a fixed arrangement or structure. This makes gases highly compressible, meaning their volume can be reduced by applying pressure.
Examples of gases include oxygen, nitrogen, carbon dioxide, and helium. They exist in various forms in our everyday lives, from the air we breathe to the gases used in cooking, heating, and industrial processes.
Question 7 Report
Which of the following factors does NOT affect the rate of a chemical reaction?
Answer Details
The factor that does NOT affect the rate of a chemical reaction is the molecular weight of products.
The rate of a chemical reaction is influenced by various factors, such as:
However, the molecular weight of products does not directly affect the rate of a chemical reaction. The rate of a reaction is determined by the characteristics of the reactants and the conditions in which the reaction takes place, not the molecular weight of the resulting products.
Question 8 Report
Which of the following statements is true regarding the melting and boiling points of pure substances?
Answer Details
The correct statement regarding the melting and boiling points of pure substances is that the melting and boiling points can vary depending on the substance.
The melting point of a substance is the temperature at which it changes from a solid to a liquid state. On the other hand, the boiling point is the temperature at which a substance changes from a liquid to a gas state.
Both melting and boiling points are unique for each substance. The melting and boiling points are influenced by the strength of the forces of attraction between the molecules or atoms that make up the substance.
Substances with strong intermolecular forces will have higher melting and boiling points, while substances with weak intermolecular forces will have lower melting and boiling points. For example, metals tend to have high melting and boiling points because the metallic bonds between the metal atoms are strong.
Ionic compounds also have high melting and boiling points because of the strong electrostatic attraction between the positively and negatively charged ions. In contrast, molecular substances generally have lower melting and boiling points because the forces of attraction between their molecules are weaker.
This is why substances like water (H2O) have lower melting and boiling points compared to metals or ionic compounds. So, to summarize, the melting and boiling points of pure substances are not always the same and can vary depending on the substance.
The strength of the intermolecular forces determines the melting and boiling points, with substances having stronger forces generally having higher melting and boiling points.
Question 9 Report
When a substance is oxidized, it
Answer Details
When a substance is oxidized, it loses electrons.
Oxidation is a chemical process in which a substance reacts with another substance or element, resulting in the loss of electrons from the oxidized substance. In other words, the oxidized substance gives away electrons to another substance or element.
This loss of electrons during oxidation is significant because electrons are negatively charged particles that play a crucial role in chemical reactions. By losing electrons, the oxidized substance becomes positively charged or oxidized.
It's important to note that oxidation doesn't necessarily involve the gain of oxygen atoms. While some reactions involving oxidation do include the addition of oxygen, it is not a defining characteristic of oxidation. The key factor is the loss of electrons, regardless of whether oxygen atoms are involved or not.
Question 10 Report
Stainless steel is an alloy made up of
Answer Details
Stainless steel is an alloy that is made up of iron and chromium.
An alloy is a mixture of two or more metals, or a metal and another element. In the case of stainless steel, it is primarily composed of iron, which is a strong and durable metal. Chromium is added to the iron to give stainless steel its unique properties.
The addition of chromium to iron results in the formation of a thin, invisible layer on the surface of the steel called chromium oxide. This layer is what gives stainless steel its corrosion-resistant properties. It creates a protective barrier that prevents the iron from reacting with oxygen and moisture in the air, which would otherwise lead to rusting.
In addition to its corrosion resistance, stainless steel is also known for its strength, durability, and aesthetic appeal. It is used in various industries, such as construction, automotive, and kitchenware, due to its ability to withstand harsh environments and maintain its appearance even with regular use.
Therefore, the correct answer is iron and chromium for the composition of stainless steel.
Question 11 Report
What is the product of the electrolysis of aqueous sodium chloride (NaCl) using inert electrodes?
Answer Details
The product of the electrolysis of aqueous sodium chloride (NaCl) using inert electrodes is Hydrogen gas at the cathode and chlorine gas at the anode.
During electrolysis, an electric current is passed through the sodium chloride solution. The solution dissociates into its ions: Na+ (sodium ion) and Cl- (chloride ion).
At the cathode (negative electrode), the positively charged sodium ions are attracted to the electrode. Since sodium is less reactive than hydrogen, it does not get discharged. Instead, hydrogen ions (H+) from the water in the solution are discharged, forming hydrogen gas (H2).
At the anode (positive electrode), the negatively charged chloride ions are attracted to the electrode. Chlorine ions (Cl-) are discharged and form chlorine gas (Cl2).
Therefore, the overall reaction can be summarized as follows:
2H2O + 2NaCl -> 2NaOH + H2 + Cl2
Question 12 Report
What is the name of the process by which ammonia is produced on an industrial scale?
Answer Details
The name of the process by which ammonia is produced on an industrial scale is called the Haber process. The Haber process is a very important chemical process that allows the production of ammonia from nitrogen and hydrogen gases. It was developed by Fritz Haber and Carl Bosch in the early 20th century and is still widely used today. In the Haber process, nitrogen gas (N2) from the air is combined with hydrogen gas (H2) obtained from natural gas or other sources. These gases are then reacted under high pressure (around 200 atmospheres) and with the help of a catalyst, usually made of iron, to form ammonia (NH3). The reaction can be represented by the following equation: N2 + 3H2 → 2NH3 The Haber process is carried out at high pressure to increase the yield of ammonia, as the reaction is favored by higher pressure. The catalyst helps to speed up the reaction and increase the efficiency of the process. Ammonia is an important chemical compound used in the production of fertilizers, cleaning products, and various other industrial processes. The Haber process plays a crucial role in meeting the global demand for ammonia and enabling the production of these essential products on a large scale. Therefore, the correct answer is the Haber process.
Question 13 Report
Why is water often referred to as the "universal solvent"?
Answer Details
Water is often referred to as the "universal solvent" because it has the ability to dissolve many different substances. This is primarily due to its polar nature.
When we say water is polar, it means that the water molecule has a slight positive charge at one end (hydrogen) and a slight negative charge at the other end (oxygen). This charge difference creates an attraction between the water molecule and other charged molecules or ions.
Because of its polar nature, water can effectively separate and surround particles or molecules of other substances, causing them to separate and disperse. This is known as dissolving. Water can dissolve many substances, including salts, sugars, acids, and many other organic and inorganic compounds.
The ability of water to dissolve so many different substances is important for several reasons. First, it allows nutrients and minerals to be transported within living organisms, facilitating biochemical reactions necessary for life.
Furthermore, water's ability to dissolve substances enables it to act as a solvent in many chemical reactions, making it essential for many industrial and biological processes. Water acts as a medium in which substances can react, allowing chemical reactions to occur efficiently.
Overall, the combination of water's abundance, essentiality for life, involvement in chemical reactions, and its ability to dissolve a wide variety of substances due to its polar nature is why water is often referred to as the "universal solvent."
Question 14 Report
Which functional group is present in alkanals?
Answer Details
The functional group present in alkanals is the carbonyl group (C=O).
In organic chemistry, functional groups are specific groups of atoms that are responsible for the characteristic chemical reactions and properties of a compound.
The carbonyl group consists of a carbon atom bonded to an oxygen atom with a double bond (C=O). It is often found at the end of the carbon chain in alkanals, which are a type of organic compound derived from alkanes.
The presence of the carbonyl group gives alkanals several important properties and reactivities. For example:
In summary, the presence of the carbonyl group (C=O) is the defining feature of alkanals, giving them specific chemical properties and reactivities.
Question 15 Report
When anhydrous cobalt chloride paper is exposed to water, what color change is observed?
Answer Details
When anhydrous cobalt chloride paper is exposed to water, the color change observed is from blue to pink.
Anhydrous cobalt chloride paper is a type of paper that contains cobalt chloride in a dry form. Cobalt chloride is a chemical compound that can exist in both anhydrous (without water) and hydrated (with water) form.
In its anhydrous form, cobalt chloride appears as blue crystals. These crystals do not contain any water molecules. When anhydrous cobalt chloride is exposed to water, it undergoes a chemical reaction called hydration.
During hydration, water molecules are absorbed by the cobalt chloride crystals, resulting in the formation of hydrated cobalt chloride. The hydrated form of cobalt chloride is pink in color.
So, when anhydrous cobalt chloride paper comes into contact with water, the blue crystals of cobalt chloride change into pink crystals of hydrated cobalt chloride. This color change is a clear indication that water is present.
Therefore, the color change observed when anhydrous cobalt chloride paper is exposed to water is from blue to pink.
Question 16 Report
Which of the following is a primary constituent of crude oil?
Answer Details
Crude oil is composed of various hydrocarbons, which are organic compounds made up of hydrogen and carbon atoms. Hydrocarbons are the primary constituents of crude oil. They can vary in size and structure, giving rise to different components of crude oil. Out of the options given, **methane** is a primary constituent of crude oil. Methane is the simplest hydrocarbon and is commonly known as natural gas. It consists of one carbon atom bonded to four hydrogen atoms (CH4). While methane is primarily associated with natural gas, it can also be found as a component of crude oil. Pentane, ethanol, and heptane are also hydrocarbons but are not considered primary constituents of crude oil. Pentane and heptane are both hydrocarbons composed of five and seven carbon atoms respectively, while ethanol is an alcohol composed of two carbon atoms, six hydrogen atoms, and one oxygen atom. To summarize, the primary constituent of crude oil is **methane**, which is a simple hydrocarbon consisting of one carbon atom and four hydrogen atoms.
Question 17 Report
According to the kinetic theory of gases, the pressure exerted by a gas is due to
Answer Details
The pressure exerted by a gas is due to the collisions of gas particles with the container walls. This is explained by the kinetic theory of gases, which provides a simple model to understand the behavior of gases. According to the kinetic theory, a gas is made up of tiny particles (such as atoms or molecules) that are in constant random motion. These particles move in straight lines until they collide with each other or with the walls of the container. When gas particles collide with the walls of the container, they exert a force on the walls. This force is what we call pressure. The more frequently and forcefully the particles collide with the walls, the greater the pressure exerted by the gas. The other options mentioned - the vibrations of gas particles, the weight of the gas particles, and the attractive forces between gas particles - are not the primary factors contributing to the pressure exerted by a gas. While these factors may play a role in certain situations, they are not the main reason for the pressure in a gas. In summary, the pressure exerted by a gas is primarily due to the collisions of gas particles with the container walls. This concept is explained by the kinetic theory of gases, which helps us understand the behavior of gases and how they exert pressure.
Question 18 Report
A gas occupies a volume of 1.5 liters at a pressure of 2 atmospheres. If the pressure is increased to 4 atmospheres while the temperature remains constant, what will be the new volume of the gas?
Answer Details
According to Boyle's law (for constant temperature), the product of initial pressure and initial volume is equal to the product of final pressure and final volume. Therefore, (1.5 liters) × (2 atmospheres) = (new volume) × (4 atmospheres). Solving for the new volume gives us (new volume) = (1.5 liters × 2 atmospheres) / 4 atmospheres = 0.75 liters.
Question 19 Report
Which of the following compounds is an example of an electrovalent bond?
Answer Details
An electrovalent bond, also known as an ionic bond, is a type of chemical bond that forms between two atoms when one atom transfers electrons to another. This creates a bond between the positively charged ion and the negatively charged ion.
Out of the given compounds, NaCl (sodium chloride) is an example of an electrovalent bond.
In NaCl, a sodium atom transfers one electron to a chlorine atom. This results in the formation of a sodium ion (Na+) and a chlorine ion (Cl-). The sodium ion has a positive charge because it lost an electron and the chlorine ion has a negative charge because it gained an electron.
The opposite charges of the sodium and chlorine ions attract each other, resulting in the formation of a strong electrovalent/ionic bond between them. This bond holds the sodium and chloride ions together to form a crystal lattice structure of sodium chloride.
On the other hand, CO2 (carbon dioxide), H2O (water), and CH4 (methane) do not involve the transfer of electrons between atoms. These compounds have covalent bonds, where electrons are shared between atoms.
Understanding the concept of electrovalent bonds is important because it helps explain the properties and behavior of ionic compounds, such as their high melting and boiling points, solubility in water, and ability to conduct electricity when dissolved or molten.
Question 20 Report
Which of the following metals is commonly alloyed with copper to make brass?
Answer Details
The metal that is commonly alloyed with copper to make brass is zinc. Brass is an alloy made by combining copper and zinc in varying proportions.
Alloys are materials made by mixing two or more metals together. By combining copper and zinc, we create brass, which has different properties than copper or zinc alone.
Zinc is chosen as the common metal to alloy with copper because it has a lower melting point and is more affordable compared to other metals like iron, nickel, or aluminum. This makes it easier and cheaper to produce brass.
Brass has many useful properties that make it a popular material for various applications. It has good corrosion resistance, making it suitable for use in plumbing fittings and musical instruments. It is also easily malleable, meaning it can be shaped into different forms without breaking.
In conclusion, zinc is commonly alloyed with copper to make brass due to its lower melting point, affordability, and the desirable properties it imparts to the alloy.
Question 21 Report
What is the molecular geometry of a molecule with three bonding pairs and no lone pairs around the central atom?
Answer Details
The molecular geometry of a molecule with three bonding pairs and no lone pairs around the central atom is trigonal planar. In a molecule, the arrangement of atoms around the central atom determines its molecular geometry. In this case, we have three bonding pairs around the central atom. To determine the molecular geometry, we use the valence shell electron pair repulsion (VSEPR) theory. According to this theory, electron pairs (both bonding and lone pairs) will arrange themselves in such a way as to minimize repulsion between them. In a trigonal planar arrangement, the three bonding pairs are arranged in a flat plane, with each bond angle being 120 degrees. This means that the central atom is surrounded by three other atoms in a triangular shape. The other options mentioned, such as tetrahedral, linear, and octahedral, do not apply to this particular scenario because they involve different numbers of bonding pairs and/or lone pairs. In summary, a molecule with three bonding pairs and no lone pairs around the central atom has a trigonal planar molecular geometry.
Question 22 Report
Which of the following methods is commonly used to remove suspended impurities from water?
Answer Details
The Filtration method is commonly used to remove suspended impurities from water.
When water is obtained from natural sources such as rivers, lakes, or groundwater, it often contains various suspended impurities. These impurities can include particles like sand, clay, silt, and organic matter. These impurities make the water cloudy or turbid and can also affect its taste and smell.
Filtration is the process of passing water through a porous material or medium to separate and remove the suspended impurities. The porous material used in filtration is typically sand, activated carbon, or a combination of different layers of materials.
As the water flows through the filtration medium, the suspended impurities get trapped and retained in the tiny pores or gaps within the material. This effectively removes the impurities from the water, resulting in clearer and cleaner water.
Filtration is a widely used method in water treatment plants, households, and industries to improve the quality of water. It is an essential step in the treatment of drinking water to ensure that it is safe for consumption.
Other methods mentioned, such as Fluoridation, Chlorination, and Distillation, serve different purposes in water treatment:
- Fluoridation: This process involves adding a controlled amount of fluoride to drinking water to help prevent tooth decay. It is not primarily used to remove suspended impurities from water. - Chlorination: This process involves adding chlorine to water to disinfect it and kill harmful microorganisms. While chlorination can help remove some suspended impurities, its main purpose is to disinfect water. - Distillation: This method involves heating water to create steam, which is then cooled and collected as purified water. Distillation is effective in removing impurities but is less commonly used on a large scale due to its energy-intensive nature.In conclusion, Filtration is the most commonly used method to remove suspended impurities from water, ensuring that it is clear, clean, and suitable for various applications.
Question 23 Report
Answer Details
When an acidic solution is diluted by adding more solvent (usually water), the concentration of hydrogen ions (H+ ) decreases. As a result, the pH of the solution decreases, making it less acidic
Question 24 Report
Which noble gas is radioactive and is produced as a decay product of uranium and thorium?
Answer Details
The noble gas that is radioactive and produced as a decay product of uranium and thorium is called Radon.
Noble gases are elements that are found in Group 18 of the periodic table. They are known for their low reactivity and tendency to not form compounds easily. Radon is the heaviest noble gas and is completely colorless, odorless, and tasteless.
Radioactive decay is a process in which the nucleus of an unstable atom releases radiation particles and energy. Uranium and thorium are both radioactive elements found in nature. As these elements undergo radioactive decay, they release various particles, including alpha particles.
Radon is produced as a decay product of the radioactive decay of uranium and thorium. It is formed when uranium and thorium atoms release an alpha particle and transform into radon atoms. This process is known as alpha decay.
Radon gas is highly radioactive and can pose health risks if inhaled in large quantities. It is a major concern as it can accumulate in confined spaces such as basements and cause long-term health problems, including an increased risk of lung cancer.
To summarize, Radon is the noble gas that is radioactive and produced as a decay product of uranium and thorium through the process of alpha decay.
Question 25 Report
Which organic compound is responsible for the characteristic aroma of fruits?
Answer Details
The organic compound responsible for the characteristic aroma of fruits is ester.
Esters are organic compounds that are formed when an alcohol reacts with an organic acid in the presence of a catalyst. They have a pleasant fruity, floral, or sweet smell, which is why they are often used in perfumes and flavorings. Esters are volatile compounds, meaning they easily evaporate and contribute to the aroma of fruits.
On the other hand, alkanes and alkynes are hydrocarbons that do not have a specific aroma. They are odorless and are typically found in substances like petroleum and natural gas.
Amines, although they can have distinct odors, are not primarily responsible for the characteristic aroma of fruits. Amines often have a fishy or ammonia-like smell and are found in substances like rotten eggs or urine.
Therefore, the correct answer is ester, as it is the organic compound that gives fruits their delightful scent.
Question 26 Report
What happens when alkanoic acids react with alcohols in the presence of an acid catalyst?
Answer Details
When alkanoic acids react with alcohols in the presence of an acid catalyst, esterification occurs.
Esterification is a chemical reaction that results in the formation of an ester. An ester is a compound that is formed by the reaction between an acid and an alcohol. In this case, the alkanoic acid and alcohol react together to form an ester.
The reaction is initiated by the acid catalyst, which helps to speed up the reaction and increase the yield of the desired ester product.
During the reaction, the acid catalyst provides a proton (H+) to the alkanoic acid, which makes it more reactive. The alcohol then attacks the carbonyl carbon of the alkanoic acid, resulting in the formation of a new bond.
The final product of the reaction is an ester, which is a compound that has an oxygen atom connected to a carbon atom through a single bond, with the other end of the oxygen atom connected to an alkyl group.
To summarize, when alkanoic acids react with alcohols in the presence of an acid catalyst, esterification occurs, resulting in the formation of an ester compound.
Question 27 Report
Which of the following methods can be used to remove temporary hardness from water?
Answer Details
One method that can be used to remove temporary hardness from water is boiling.
When water is heated and boiled, it causes the dissolved minerals that contribute to temporary hardness, such as calcium and magnesium bicarbonates, to precipitate out of the water. These precipitates settle at the bottom of the container or can be filtered out, resulting in the removal of temporary hardness.
Filtration can also help in removing temporary hardness from water. This method involves passing water through a filter that is designed to trap and remove the dissolved mineral ions responsible for hardness. The filter can be made of materials like activated carbon or ion-exchange resin, which have the ability to bind with calcium and magnesium ions and remove them from the water.
Distillation is another effective method for removing temporary hardness from water. Distillation involves heating the water to boiling point, and then collecting and condensing the steam to obtain pure water. As the water is heated and evaporates, the dissolved minerals are left behind, resulting in the separation of the excess minerals and the production of softened water.
Chlorination is not a method that can be used to remove temporary hardness from water. Chlorination refers to the process of adding chlorine or chlorine compounds to water to disinfect and kill harmful microorganisms. It does not have any direct effect on the mineral content of the water, and therefore cannot remove temporary hardness.
In summary, methods such as boiling, filtration, and distillation can be used to remove temporary hardness from water, while chlorination does not have any impact on hardness removal.
Question 28 Report
What is the atomic number of aluminium?
Answer Details
The atomic number of aluminium is 13.
Each atom of an element is uniquely identified by its atomic number. The atomic number represents the number of protons found in the nucleus of an atom. In the case of aluminium, it has 13 protons in its nucleus.
The atomic number is a fundamental property of an element and helps in organizing the elements in the periodic table. It provides information about the position of the element in the periodic table and its chemical characteristics.
In summary, aluminium has an atomic number of 13, which signifies that it has 13 protons in its nucleus.
Question 29 Report
Isotopes of an element have
Answer Details
Isotopes of an element have the same number of protons (which defines the element) but may have different numbers of neutrons. Since atoms are electrically neutral, the number of protons must equal the number of electrons in an atom.
Question 30 Report
What is the trend for ionization energy across a period in the periodic table?
Answer Details
The trend for ionization energy across a period in the periodic table is that it increases from left to right. Ionization energy is the energy required to remove an electron from an atom or ion. When moving from left to right across a period, the number of protons in the nucleus increases, which means there is a stronger attractive force on the electrons. As a result, it becomes more difficult to remove an electron and the ionization energy increases. Therefore, the correct option is that the ionization energy increases from left to right across a period in the periodic table.
Question 31 Report
What is the main source of carbon monoxide (CO) in urban areas?
Answer Details
The main source of carbon monoxide (CO) in urban areas is vehicle emissions.
When vehicles burn fuel, such as gasoline or diesel, they produce a variety of air pollutants, including carbon monoxide. This occurs because the fuel combustion process is not completely efficient, resulting in the release of carbon monoxide gas into the air.
Vehicle emissions are a significant contributor to air pollution in urban areas, especially in densely populated cities where there is a high concentration of vehicles. The exhaust from cars, trucks, buses, and motorcycles contributes to the elevated levels of carbon monoxide in the surrounding air.
Carbon monoxide is a colorless and odorless gas that is harmful to human health. It can be particularly dangerous in enclosed spaces, as it can build up to toxic levels and interfere with the body's ability to carry oxygen to vital organs.
To reduce the levels of carbon monoxide in urban areas, it is important to implement measures such as adopting cleaner transportation technologies, promoting public transportation, and improving vehicle emission standards. These efforts can help mitigate the negative impacts of carbon monoxide on air quality and public health.
Question 32 Report
Which type of salt is found in antacid medications and is used to relieve heartburn and indigestion?
Answer Details
The type of salt found in antacid medications to relieve heartburn and indigestion is magnesium chloride.
Magnesium chloride is used as an active ingredient in antacids because it has the ability to neutralize excess stomach acid. When you have heartburn or indigestion, it means that there is too much acid in your stomach, causing discomfort and a burning sensation.
Magnesium chloride works by reacting with the excess stomach acid to form magnesium hydroxide. This compound, magnesium hydroxide, is a strong base that can effectively neutralize the acid, reducing the symptoms of heartburn and indigestion.
By taking antacid medications that contain magnesium chloride, you can help to balance the acidity in your stomach and provide relief from the discomfort caused by excess acid.
Question 33 Report
Benzene can be converted to its derivative toluene by the addition of a methyl group. The reaction is an example of
Answer Details
The reaction where benzene is converted to toluene by the addition of a methyl group is an example of electrophilic substitution. In electrophilic substitution reactions, a hydrogen atom in the benzene ring is replaced by an electrophile (electron deficient species) to form a new compound.
Here, the methyl group is the electrophile that replaces one of the hydrogen atoms in the benzene ring, resulting in the formation of toluene.
During the reaction, the benzene ring undergoes a series of steps:
Therefore, the addition of a methyl group to benzene to form toluene is an example of electrophilic substitution.
Question 34 Report
Sodium reacts vigorously with water to produce
Answer Details
When sodium reacts with water, it undergoes a very vigorous reaction. This means that the reaction is very fast and produces a lot of energy. The products that are formed during this reaction are sodium hydroxide (NaOH) and hydrogen gas (H2). Let's break down the reaction step by step: 1. Sodium (Na) is a highly reactive metal. When it is placed in water (H2O), it reacts with the water molecules. 2. The sodium atom loses an electron, becoming a positively charged sodium ion (Na+). This electron is transferred to a water molecule, causing it to split apart. 3. The water molecule (H2O) is made up of two hydrogen atoms and one oxygen atom. The hydrogen ions (H+) from the water combine with the remaining electron to form hydrogen gas (H2). 4. The remaining hydroxide ions (OH-) from the water combine with the sodium ions (Na+) to form sodium hydroxide (NaOH). In summary, when sodium reacts with water, it produces sodium hydroxide (NaOH) and hydrogen gas (H2). Therefore, the correct answer is sodium hydroxide (NaOH) and hydrogen gas (H2).
Question 35 Report
What is eutrophication?
Answer Details
Eutrophication is the excessive growth of algae in water bodies, such as lakes, rivers, and oceans, due to an increase in nutrients in the water. These nutrients, mainly nitrogen and phosphorus, come from various sources including agricultural runoff, wastewater discharge, and soil erosion.
When there is an excess of nutrients in the water, it acts as a fertilizer for algae and other aquatic plants. These plants grow rapidly and form dense colonies on the water surface, resulting in what we commonly call an "algal bloom".
During the algal bloom, the water becomes green or murky and can sometimes emit an unpleasant odor. This excessive growth of algae can have several negative impacts on the aquatic ecosystem.
As the algae die and decompose, they consume a large amount of oxygen from the water, leading to oxygen depletion. This reduction in oxygen levels can be harmful to fish and other organisms that depend on oxygen to survive. It can lead to the death of fish and other aquatic organisms, creating what is known as a "dead zone".
Furthermore, the dense layer of algae on the water surface can block sunlight from penetrating into the water, limiting photosynthesis for other aquatic plants and organisms. This can disrupt the balance of the ecosystem, affecting the biodiversity of the water body.
In summary, eutrophication is caused by an excess of nutrients in the water, leading to the rapid growth of algae and the subsequent negative impacts on oxygen levels and biodiversity in the aquatic ecosystem.
Question 36 Report
What type of reaction is involved in the formation of alkanols from alkenes?
Answer Details
The reaction involved in the formation of alkanols from alkenes is called addition reaction.
In an addition reaction, two reactants combine together to form a larger product molecule. In this case, the alkene (a hydrocarbon with a carbon-carbon double bond) reacts with a molecule of water (H2O) to form an alkanol (an alcohol).
During the reaction, the carbon-carbon double bond in the alkene breaks, and each carbon atom bonds to a hydrogen atom from the water molecule.
This results in the formation of a single bond between the carbon atoms and a bond between each carbon atom and a hydrogen atom.
The remaining oxygen and hydrogen atoms from the water molecule form a hydroxyl group (-OH) on one of the carbon atoms. This addition reaction is a way to introduce an -OH group and create an alcohol from an alkene.
It is important to note that alkanols are a specific type of alcohol where the hydroxyl group is attached to a saturated carbon atom (a carbon atom bonded to four other atoms).
Therefore, the correct answer is addition reaction.
Question 37 Report
Which of the following is a common laboratory indicator for bases?
Answer Details
A laboratory indicator is a substance that changes color in the presence of an acid or a base. It helps us determine the nature of a solution, whether it is acidic or basic.
Out of the given options, Phenolphthalein is a common laboratory indicator for bases.
Phenolphthalein is a colorless compound that turns pink or purple in the presence of a base. It is widely used because it has a clear and distinct color change, making it easy to identify the presence of a base. When a base is added to a solution containing phenolphthalein, the compound undergoes a chemical reaction and changes its structure, resulting in a change in color.
Methyl orange, on the other hand, is a laboratory indicator for acids. It changes color in the presence of an acid but remains unchanged in the presence of a base.
Bromothymol blue is another laboratory indicator commonly used to test for acids and bases. It turns yellow in the presence of an acid and blue in the presence of a base.
Litmus is a natural dye extracted from lichens. It is a general indicator that turns red in the presence of an acid and blue in the presence of a base.
However, out of the options provided, Phenolphthalein is the specific laboratory indicator commonly used to test for bases.
Question 38 Report
What is the IUPAC name for the compound CCl4 ?
Answer Details
The IUPAC name for the compound CCl4 is tetrachloromethane
Question 39 Report
What is the sum of the oxidation numbers in a neutral compound?
Answer Details
The sum of the oxidation numbers in a neutral compound is always equal to zero.
Oxidation numbers are assigned to each element in a compound to indicate the redistribution of electrons during a chemical reaction.
The oxidation number represents the charge an atom would have if electrons were transferred completely.
In a neutral compound, the total positive charges must balance the total negative charges. Since electrons are neither gained nor lost in a neutral compound, the sum of the oxidation numbers must equal zero.
Therefore, the answer is 0.
Question 40 Report
Which transition metal is known for its multiple colorful oxidation states and compounds used in pigments and paints?
Answer Details
The transition metal that is known for its multiple colorful oxidation states and compounds used in pigments and paints is copper (Cu). Copper is an element that belongs to the transition metal group in the periodic table. Transition metals are known for their ability to have multiple oxidation states, meaning they can gain or lose different numbers of electrons when forming chemical compounds. What makes copper particularly interesting is that it can form compounds with a range of oxidation states, including +1, +2, and +3. Each of these oxidation states gives copper a unique color, and this is why it is commonly used in pigments and paints to achieve a variety of vibrant hues. In its +1 oxidation state, copper compounds appear as a pale blue color. This form of copper is often called "cuprous" and is used in the production of blue pigments. One example is Egyptian blue, which was widely used in ancient artwork. In its +2 oxidation state, copper compounds have a greenish color. This is the most common oxidation state for copper and is responsible for the green patina that forms on copper surfaces, such as statues and roofs, over time. It is also used in the production of green pigments, including verdigris. Lastly, in its +3 oxidation state, copper compounds can appear in various shades of blue and green. This oxidation state is less common but still plays a role in the production of pigments and paints. Overall, the ability of copper to exhibit multiple colorful oxidation states makes it a highly desirable choice for creating a wide range of pigments and paints that add vibrancy and visual appeal to various artistic and decorative applications.
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