JAMB UTME - Chemistry - 2023

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:

• Polarity: The presence of the highly electronegative oxygen atom in the carbonyl group creates a significant dipole moment, making the molecule polar.
• Oxidation: The carbonyl group is easily oxidized, leading to the formation of carboxylic acids.
• Nucleophilic addition: The carbon atom of the carbonyl group can undergo nucleophilic addition reactions, leading to the formation of new bonds with nucleophiles.

In summary, the presence of the carbonyl group (C=O) is the defining feature of alkanals, giving them specific chemical properties and reactivities.

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.

The common name for ethanoic acid is acetic acid.

Acetic acid is a clear, colorless liquid with a strong, pungent odor. It is a weak acid commonly found in vinegar, giving it its sour taste and distinct smell. Acetic acid is also used in many industries, such as food production, pharmaceuticals, and cleaning products.

The name "acetic acid" is derived from the Latin word "acetum," which means vinegar. This is because acetic acid is the main component of vinegar.

In summary, the common name for ethanoic acid is acetic acid, which is a weak acid found in vinegar and used in various industries.

At room temperature and standard pressure, chlorine gas is in the state of matter called gas.

In chemistry, there are three main states of matter: solid, liquid, and gas. The state of matter depends on the arrangement and movement of the particles that make up a substance.

Let's consider each state of matter one by one:

Solid: In a solid state, the particles are tightly packed together and have fixed positions. They vibrate in place but do not move around freely. Solids have a definite shape and volume. Examples of solids are a desk, a brick, or a piece of ice.

Liquid: In a liquid state, the particles are more spread out compared to solids. They have some freedom to move, but they still remain close to each other. Liquids can flow and take the shape of the container they are in. However, they still have a definite volume. Examples of liquids are water, milk, or oil.

Gas: In a gas state, the particles are far apart and move freely in all directions. They have much more energy compared to particles in solids or liquids. Gases do not have a definite shape or volume and can expand to fill the entire space they are contained in. Examples of gases are air, oxygen, or carbon dioxide.

Chlorine gas, at room temperature and standard pressure, exists as individual chlorine molecules that are far apart and move freely. Therefore, it is classified as a gas.

The highest entropy change would be expected in the Liquid → Gas reaction.

Entropy is a measure of the disorder or randomness in a system. When a substance changes from a state of lower disorder to a state of higher disorder, its entropy increases.

In the Liquid → Gas reaction, the substance is changing from a liquid state (where the particles are more closely packed and have less freedom of movement) to a gas state (where the particles are more spread out and have more freedom of movement).

As the particles transition from being tightly packed in the liquid phase to being more spread out in the gas phase, their randomness increases. This increase in randomness leads to an increase in entropy.

Therefore, the Liquid → Gas reaction would be expected to have the highest entropy change among the given options.

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.

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.

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.

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.

The trace gas in the atmosphere that plays a significant role in the greenhouse effect is carbon dioxide.

The greenhouse effect is a natural process that helps to regulate the Earth's temperature. When sunlight reaches the Earth's surface, some of it is absorbed and warms the planet. However, some of this heat is also radiated back into space.

Greenhouse gases, such as carbon dioxide, trap some of this heat and prevent it from escaping into space. They act like a blanket around the Earth, keeping it warm. Without these greenhouse gases, the Earth would be much colder and life as we know it would not be possible.

However, human activities, such as burning fossil fuels like coal, oil, and natural gas, have been increasing the concentration of carbon dioxide in the atmosphere. This excessive amount of carbon dioxide has enhanced the greenhouse effect, leading to global warming.

Global warming is the long-term increase in Earth's average temperature due to the increased levels of greenhouse gases. It is causing changes in climate patterns, melting of polar ice caps, rising sea levels, and extreme weather events.

So, in summary, carbon dioxide is the trace gas in the atmosphere that plays a significant role in the greenhouse effect and contributes to global warming.

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.

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.

The position of equilibrium shifts to the left.

The valency of an element is a measure of its ability to combine with other elements to form compounds. It is determined by the number of electrons an atom can gain, lose, or share in order to achieve a stable electronic configuration.

In the given electronic configuration 2, 8, 7, the element has a total of 17 electrons. In order to achieve a stable electronic configuration, the element needs to either gain one electron to complete its outermost shell or lose seven electrons to empty its outermost shell.

The valency of an element is typically determined by the number of electrons in its outermost shell, also known as the valence shell. In this case, the element has 7 electrons in its valence shell, which means it needs to gain one electron to achieve a stable configuration.

Therefore, the valency of the element with the electronic configuration 2, 8, 7 is 1, as it needs to gain one electron to achieve stability.

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."

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.

An element with an atomic number of 8 and a mass number of 16 has 8 neutrons.

Let's break down the information to understand why.

The atomic number of an element tells you the number of protons in its nucleus. In this case, the element has an atomic number of 8, which means it has 8 protons.

The mass number of an element is the sum of its protons and neutrons. In this case, the mass number is 16.

To calculate the number of neutrons, we subtract the atomic number from the mass number: Number of Neutrons = Mass Number - Atomic Number

So, in this case, the number of neutrons would be: 16 (mass number) - 8 (atomic number) = 8 neutrons.

Therefore, the element in question has 8 neutrons.

The type of chemical combination that involves the transfer of electrons from one atom to another, resulting in the formation of oppositely charged ions, is ionic bonding.

In an ionic bond, one atom donates electrons to another atom. This happens when one atom has a stronger attraction for electrons than the other. The atom that donates electrons becomes positively charged (known as a cation), while the atom that receives the electrons becomes negatively charged (known as an anion).

The transfer of electrons occurs because atoms want to achieve a stable electron configuration, usually by having a complete outermost electron shell. By transferring electrons, atoms can achieve this stability. The resulting oppositely charged ions are attracted to each other due to the electrostatic force, forming an ionic bond.

For example, in the formation of table salt (sodium chloride), sodium (Na) donates an electron to chlorine (Cl). Sodium becomes a positively charged ion (Na+), and chlorine becomes a negatively charged ion (Cl-). The positive and negative charges attract each other, creating the ionic bond in sodium chloride.

Overall, ionic bonding involves the transfer of electrons, resulting in the formation of oppositely charged ions. This type of chemical combination is an essential concept in understanding various compounds and their properties.

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.

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.

A common property of non-metals is that they tend to gain electrons in chemical reactions.

Non-metals are a group of elements on the periodic table that have certain characteristics in common. One of these characteristics is their tendency to gain electrons during chemical reactions.

Electrons are negatively charged particles that orbit around the nucleus of an atom. Non-metals have a higher attraction for electrons compared to metals. This means that when non-metals come into contact with other elements, they have a greater likelihood of taking electrons from those elements.

This process of gaining electrons is called electron gainor electron capture. When non-metals gain electrons, they become negatively charged ions, also known as anions. This electron gain gives them stability and helps them achieve a full outer electron shell, similar to the noble gases.

The tendency of non-metals to gain electrons is an essential characteristic that distinguishes them from metals. Metals, on the other hand, tend to lose electrons during chemical reactions, leading to the formation of positively charged ions called cations.

Therefore, the property that matches the description is "Tend to gain electrons in chemical reactions," making it a common characteristic of non-metals.

The process of rusting is an example of the formation of an acidic oxide.

Rusting occurs when iron or steel react with oxygen and moisture in the presence of an electrolyte (such as water or salt). This reaction forms a reddish-brown substance called rust.

Rust is considered an acidic oxide because it reacts with water to form an acid. When moisture is present, iron reacts with oxygen to create iron(III) oxide, which is the main component of rust. This iron oxide reacts further with water to produce hydrated iron(III) oxide and releases H+ ions, making the resulting solution acidic.

For example, the reaction between iron, oxygen, and water can be represented by the following equations:

Iron + Oxygen → Iron(III) Oxide

Fe + O2 → Fe2O3

Iron(III) Oxide + Water → Hydrated Iron(III) Oxide + Acid

Fe2O3 + xH2O → Fe2O3·xH2O + H+

Therefore, it is clear that the formation of rust is an example of the formation of an acidic oxide.

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:

1. An electrophile, in this case, the methyl group, is attracted to the electron-rich benzene ring.
2. The electrophile forms a bond with one of the carbon atoms in the benzene ring, breaking the aromaticity of the ring.
3. This leads to the formation of a sigma complex, where the electrophile is attached to the benzene ring.
4. Finally, the sigma complex is converted back into an aromatic compound by the loss of a proton, resulting in the formation of toluene.

Therefore, the addition of a methyl group to benzene to form toluene is an example of electrophilic substitution.

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.

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.

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:

• Concentration of reactants: Increasing the concentration of reactants leads to more frequent collisions between particles, resulting in a higher reaction rate. The greater the concentration, the faster the reaction.
• Presence of a catalyst: A catalyst is a substance that speeds up a chemical reaction without being consumed itself. It provides an alternative reaction pathway with a lower activation energy, allowing the reaction to occur more easily and quickly.
• Temperature: Increasing the temperature increases the kinetic energy of the reactant particles. This leads to more frequent and energetic collisions, increasing the likelihood of successful collisions and accelerating the reaction rate.

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.

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.

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.