JAMB UTME - Chemistry - 2018
Frage 1 Bericht
In the preparation of oxygen by heating KCIO, in the presence of MnO2 only moderate heat is needed because the catalyst acts by 2
Antwortdetails
The presence of MnO2 acts as a catalyst in the reaction of KCIO2 to produce oxygen. A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the reaction itself. MnO2 acts by lowering the energy barrier of the reaction, which means it reduces the amount of energy required for the reaction to take place. This makes it easier for the reaction to occur, and thus the reaction proceeds at a faster rate. As a result, only moderate heat is needed to provide the initial energy required for the reaction to start. Therefore, the correct answer is: lowering the energy barrier of the reaction.
Frage 2 Bericht
The solubility of the solids that dissolves in a given solvent with the liberation of heat will
Antwortdetails
The solubility of solids in a given solvent is the amount of solid that can dissolve in the solvent to form a solution. When a solid dissolves in a solvent, it releases heat. The solubility of the solid in the solvent can be affected by changes in temperature. Generally, when the temperature of a solution increases, the solubility of the solid in the solvent increases as well. This is because the increased heat energy makes it easier for the solid particles to separate and dissolve in the solvent. As a result, the solubility of the solid in the solvent will increase with an increase in temperature. On the other hand, if the temperature decreases, the solubility of the solid in the solvent decreases. This is because the decreased heat energy makes it harder for the solid particles to separate and dissolve in the solvent. As a result, the solubility of the solid in the solvent will decrease with a decrease in temperature. In summary, the solubility of solids in a given solvent will generally increase with an increase in temperature and decrease with a decrease in temperature.
Frage 3 Bericht
The ionic radii of metals are usually
Antwortdetails
The ionic radii of metals are usually smaller than their atomic radii. The size of an atom is determined by the distance between the nucleus and the outermost electrons, which is known as the atomic radius. When a metal atom loses one or more electrons to form a positive ion (or cation), the resulting ion has a smaller size than the original atom. This is because the positive charge of the ion attracts the remaining electrons closer to the nucleus, making the ion smaller in size. So, when a metal forms a cation, its ionic radius is typically smaller than its atomic radius. This is a general trend in the periodic table, although there are some exceptions.
Frage 4 Bericht
In the reaction between sodium hydroxide and sulphuric acid solutions, what volume of 0.5 molar sodium hydroxide would exactly neutralise 10cm3 of 1.25 molar sulphuric acid?
Frage 5 Bericht
Aluminium does not react with either dilute or concentrated trioxonitrate (V) acid because
Frage 6 Bericht
If the molecular mass of tetraoxosulphate (VI) acid is 98, calculate its vapour density
Frage 7 Bericht
Which of these alloys contains copper?
Antwortdetails
Bronze is the alloy that contains copper. Bronze is a metal alloy composed of copper and typically other elements such as tin, aluminum, silicon, or nickel. It is known for its strength, durability, and corrosion resistance. In fact, bronze is one of the earliest alloys created by humans, and it has been used for thousands of years to make tools, weapons, and decorative objects. Solder is an alloy of lead, tin, and sometimes other metals that is used to join metals together by melting the solder and allowing it to flow into the joint. Steel is an alloy of iron and carbon, and sometimes other elements like chromium, nickel, or manganese, that is known for its strength and durability. Permallory is a nickel-iron alloy with high magnetic permeability and low coercive force, which makes it useful in the production of electrical and electronic equipment. None of these alloys contain copper.
Frage 8 Bericht
The radio isotope used in industrial radiography for the rapid checking of faults in welds and casting is?
Frage 9 Bericht
H2 S(g) + Cl2(g) → 2HCl(g) + S(g) In the reaction above, the substance that is reduced is
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Frage 10 Bericht
The hydrogen ion concentration of a sample of orange juice is 2.0 X 10−11 moldm−3 . What is its pOH ? [log102 = 0.3010]
Frage 11 Bericht
An aqueous solution of a metal salt, M. gives a white precipitate with NaOH which dissolves in excess NaOH. With aqueous ammonia, the solution of M also gives a white precipitate which dissolves in excess ammonia Therefore the cation in M is
Frage 12 Bericht
The derivative of benzene that can be used in making explosives is
Frage 13 Bericht
When large hydrocarbon molecules are heated at high temperature in the presence of a catalyst to give smaller molecules, the process is known as
Antwortdetails
The process of breaking down large hydrocarbon molecules into smaller molecules by heating them at high temperatures in the presence of a catalyst is known as cracking. This process is used to convert heavy, high-molecular-weight hydrocarbon molecules into lighter, more valuable products such as gasoline and diesel fuel. The high temperatures cause the large molecules to break apart into smaller ones, and the catalyst helps speed up the reaction. This process is important in the petrochemical industry, as it allows for the production of a wider range of useful products from crude oil.
Frage 14 Bericht
In the upper atmosphere, the ultra-violet light breaks off a free chlorine atom from chlorofluorocarbon molecule. The effect of this is that the free chlorine atom will
Antwortdetails
The free chlorine atom that breaks off from a chlorofluorocarbon molecule will be very reactive and will attack ozone in the upper atmosphere. Ozone is a molecule made up of three oxygen atoms, and when the free chlorine atom reacts with ozone, it breaks the ozone molecule into two separate oxygen molecules. This reaction reduces the amount of ozone in the atmosphere, which is known as ozone depletion. Over time, this can lead to a thinning of the ozone layer, which protects life on Earth from harmful ultraviolet radiation from the sun.
Frage 15 Bericht
What is the PH of 0.00 1 moldm3 solution of the sodium hydroxide
Frage 16 Bericht
Which of the following pairs of substances will react further with oxygen to form a higher oxide?
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Frage 17 Bericht
The figure above shows the electrolysis of molten sodium chloride. Z is the
Antwortdetails
The figure shows the electrolysis of molten sodium chloride. During electrolysis, an electric current is passed through a molten or dissolved ionic compound to separate the ions. The positive ions move towards the negative electrode (cathode) and the negative ions move towards the positive electrode (anode). In the figure, the electrode connected to the positive terminal of the battery is the anode and the electrode connected to the negative terminal is the cathode. At the anode, the negatively charged chloride ions (Cl-) lose electrons and are oxidized to form chlorine gas (Cl2). At the cathode, the positively charged sodium ions (Na+) gain electrons and are reduced to form liquid sodium metal (Na). Therefore, the answer is (a) anode where the Cl- ions are oxidized. Z is the anode in the figure.
Frage 18 Bericht
Methanoic acid mixes with water in all proportions and has about the same boiling point as water. Which of the following methods would you adopt to obtain pure water from a mixture of Sand, water and methanoic acid?
Frage 19 Bericht
In electrovalency, the oxidation number of the participating metal is always
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Frage 20 Bericht
Which of the following is used to power steam engines?
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Coal is the fuel that is typically used to power steam engines. Coal is burned in a furnace to heat water and produce steam, which is then used to power a steam engine. The steam engine converts the energy from the steam into mechanical energy, which can be used to power machines or generate electricity. Coal is a fossil fuel that has been used for centuries as a source of energy, and it played a significant role in the industrial revolution, powering steam engines that were used to drive machines in factories and transport goods and people by train. Today, steam engines are less common as other forms of energy have taken their place, but they remain an important part of our history and technological development.
Frage 21 Bericht
Which of the following metals cannot replace hydrogen from water or steam?
Frage 22 Bericht
The alkanoic acid found in human sweat is
Antwortdetails
The alkanoic acid found in human sweat is CH3CH2COOH, also known as propionic acid. Sweat is composed of various substances such as water, electrolytes, and waste products. One of these waste products is an oily substance called sebum, which is secreted by the sebaceous glands in the skin. When sebum breaks down, it forms various fatty acids, including propionic acid. Propionic acid has a slightly pungent odor, which is why sweat can sometimes smell sour or cheesy. However, the presence of propionic acid in sweat is actually beneficial, as it has antimicrobial properties that help to prevent the growth of harmful bacteria on the skin. In summary, the alkanoic acid found in human sweat is propionic acid, which is a fatty acid produced when sebum breaks down. Its antimicrobial properties help to keep the skin healthy.
Frage 23 Bericht
Elements P, Q, R, S have 6, 11, 15, 17 electrons respectively, therefore,
Antwortdetails
Elements form bonds with other elements in order to attain a stable electron configuration, like the one found in noble gases. There are two types of bonds: covalent and ionic (also called electrovalent). In covalent bonds, two elements share electrons to attain a stable electron configuration. This type of bond is formed between two non-metal elements. In ionic bonds, one element donates electrons to another element, creating ions. This type of bond is formed between a metal and a non-metal element. Based on the information given, we can deduce the following: - P is a metal, as it has only 6 electrons. - Q is a non-Metal, as it has 11 electrons. - R is a metal, as it has 15 electrons. - S is a non-Metal, as it has 17 electrons. So, from this information, we can conclude that: - P will form an ionic bond with R, as P is a metal and R is a metal. - Q will form a covalent bond with S, as Q is a non-Metal and S is a non-Metal. Therefore, the correct answer is "Q will form a covalent bond with S."
Frage 24 Bericht
In the laboratory preparation of oxygen, the gas cannot be collected by displacement of air because
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Frage 25 Bericht
Calculate the pH of 0.05 moldm?3 H2 SO4
Antwortdetails
To solve this problem, we need to use the formula for calculating the pH of a solution, which is: pH = -log[H+] where [H+] is the concentration of hydrogen ions in moles per liter. The given chemical equation is: H2SO4 + 2H2O → 2H3O+ + SO42- From this equation, we can see that one molecule of sulfuric acid (H2SO4) can donate two hydrogen ions (H+) to the solution, which means that the concentration of hydrogen ions is twice the concentration of sulfuric acid. Therefore, the concentration of hydrogen ions in this solution is: [H+] = 2 x 0.05 moldm^-3 = 0.1 moldm^-3 Now we can use the formula for pH: pH = -log[H+] pH = -log(0.1) pH = 1.00 Therefore, the pH of the solution is 1.00.
Frage 27 Bericht
Sieving is a technique used to separate mixtures containing solid particles of
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Sieving is a technique used to separate mixtures containing solid particles of different sizes. A sieve is a mesh or perforated screen that is used to separate particles based on their size. The mixture is poured onto the sieve, and the particles that are too large to pass through the holes are left on top, while the smaller particles fall through the holes and are collected below. This process allows for the separation of the different-sized particles, making it easier to purify or further process the mixture.
Frage 28 Bericht
The presence of ammonia gas in a desiccator can exclusively be removed by
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Frage 29 Bericht
The number of electrons in the valence shell of an element of atomic number 14 is?
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The number of electrons in the valence shell of an element can be determined by using the periodic table and the electron configuration of the element. The valence shell is the outermost shell that contains electrons that are involved in chemical reactions. For an element with atomic number 14, which is silicon, the electron configuration is 1s2 2s2 2p6 3s2 3p2. The valence shell of silicon is the third shell, which contains 3s2 and 3p2 electrons. Therefore, the number of electrons in the valence shell of silicon is 4 electrons.
Frage 32 Bericht
The situation obtained when a perfect gas expands into a vacuum is
Frage 33 Bericht
Which of the following are mixtures?
I. Petroleum
II. Rubber latex
III. Vulcanizer's solution
IV. Carbon sulphide
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Frage 34 Bericht
2SO2 (g) + O2 (g) ↔ 2SO3 (g) ΔH = -395.7kJmol−1
In the equation, an increase in temperature will shift the equilibrium position to the
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Frage 35 Bericht
3H2(g) + N2 ⇔ 2NH3(g) ; H= -ve
In the reaction above, lowering of temperature will
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Frage 37 Bericht
An element used in the production of matches is
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The element used in the production of matches is sulphur. Matches are small sticks made of wood or cardboard with a chemical mixture at one end. This chemical mixture, called the match head, contains several compounds including sulphur. When the match is struck against a rough surface, the friction generates heat that ignites the sulphur in the match head, causing a flame. This flame then ignites the other compounds in the match head, which in turn ignites the wood or cardboard stick. Sulphur is an important component of the match head because it is highly flammable and burns easily. It also helps to ignite the other compounds in the match head. However, sulphur by itself is not a good fuel, which means that it cannot sustain a flame on its own. Therefore, it needs other combustible materials, such as potassium chlorate or phosphorus, to make the match head burn. Overall, sulphur plays a crucial role in the chemistry of matches and allows us to easily start fires for various purposes.
Frage 38 Bericht
The general formula of alkanones is
Frage 39 Bericht
The refreshing and characteristic taste of soda water and other soft drinks is as a result of the presence of
Frage 40 Bericht
Which of the following statements is correct about the periodic table?
