JAMB UTME - Chemistry - 2011

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Chlorine gas is a strong oxidizing agent, which means it can take electrons from other substances. When chlorine gas is dissolved in water, it reacts with the water molecules to form hypochlorous acid and hydrochloric acid. Hypochlorous acid is a powerful oxidizing agent and can break down the color molecules in stains, thus "bleaching" them. Therefore, the bleaching action of chlorine gas is effective due to the presence of water.

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A deliquescent compound is a compound that readily absorbs moisture from the atmosphere and forms a solution. From the given options, only CaCl2 is a deliquescent compound. Therefore, the answer is CaCl2.

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The laboratory preparation of chlorine gas often produces impurities which need to be removed before the gas can be used. The question asks which substance is used to remove these impurities. The correct answer is not explicitly stated in the question, but can be determined through knowledge of chemistry. Chlorine gas is often prepared by reacting hydrochloric acid (HCl) with manganese dioxide (MnO2). However, impurities such as excess hydrochloric acid, water, and other gases may be present in the resulting gas mixture. To remove these impurities, a substance that can react with them must be used. Hydrogen peroxide (H2O2) or sodium hydroxide (NaOH) may be used to remove excess hydrochloric acid. Calcium carbonate (CaCO3) or sodium carbonate (Na2CO3) may be used to remove acidic gases such as carbon dioxide (CO2) and sulfur dioxide (SO2). Water may be removed by passing the gas through a drying agent such as concentrated sulfuric acid (H2SO4) or calcium chloride (CaCl2). Based on the given options, the most appropriate answer is "H2O".

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The atomic number of an element is equal to the number of protons in its nucleus. Therefore, if an isotope has an atomic number of 15, it means it has 15 protons. The mass number of an isotope is equal to the total number of protons and neutrons in its nucleus. The question states that the isotope has a mass number of 31. So, we can write: mass number = number of protons + number of neutrons 31 = 15 + number of neutrons To solve for the number of neutrons, we can subtract 15 from both sides: 31 - 15 = 15 + number of neutrons - 15 16 = number of neutrons Therefore, the isotope with an atomic number of 15 and a mass number of 31 contains 15 protons. Answer is correct.

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Sodium aluminate (III) is important in water treatment because it causes coagulation. Coagulation is the process of removing suspended particles from water by causing them to stick together and form larger particles that can be easily removed. Sodium aluminate (III) is added to water to create positively charged particles, which attract and bind with negatively charged particles in the water. This causes the suspended particles to clump together and settle at the bottom, making it easier to remove them from the water. Therefore, sodium aluminate (III) helps to improve the quality of water by making it cleaner and safer to use.

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The molecular lattice of iodine is held together by van der Waal's forces. Iodine is a diatomic molecule made up of two iodine atoms. The atoms are held together by a covalent bond formed by sharing electrons between them. In the solid state, the iodine molecules are arranged in a lattice structure held together by weak intermolecular forces called van der Waal's forces. These forces arise due to temporary fluctuations in the electron density around the atoms, which induce dipole moments in neighboring molecules. The dipole moments attract each other, creating a weak force that holds the molecules together in the lattice structure. Therefore, out of the options given, van der Waal's forces are responsible for holding the molecular lattice of iodine together.

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2-methylpropane and butane are both hydrocarbons, but they differ in their structures. 2-methylpropane has a branched chain structure while butane has a straight chain structure. 1. The statement "They are members of the same homologous series" is true. They both belong to the alkane homologous series, which is characterized by hydrocarbons with only single covalent bonds. 2. The statement "They have the same boiling point" is false. Boiling points of hydrocarbons increase as the number of carbon atoms in the molecule increases. Butane has a higher boiling point than 2-methylpropane because it has more carbon atoms in its structure, and therefore has stronger intermolecular forces of attraction. 3. The statement "They have different number of carbon atoms" is true. Butane has four carbon atoms in its structure while 2-methylpropane has only three. 4. The statement "They have the same chemical properties" is false. While they both belong to the same homologous series and have similar chemical properties, their different structures affect their reactivity. For example, 2-methylpropane may undergo different reactions than butane due to the presence of a branching in its structure.

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The question is asking to identify the option that is NOT an alkali. An alkali is a base that dissolves in water to form a solution with a pH greater than 7. Therefore, we need to identify the option that is not a base or does not dissolve in water to form a solution with a pH greater than 7. Among the options provided, the only option that is NOT an alkali is NH3. NH3 is ammonia, which is a gas at room temperature and does not dissolve in water to form a solution with a pH greater than 7. Therefore, the correct answer is NH3.

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Element X has atomic number 12, which means it has 12 protons in its nucleus. This also means that it has 12 electrons in its neutral state. Element Y has atomic number 17, which means it has 17 protons in its nucleus. This also means that it has 17 electrons in its neutral state. To determine the type of bond between X and Y, we need to look at their electronegativity values. Electronegativity is the tendency of an atom to attract electrons towards itself in a chemical bond. X is a metal element and generally has low electronegativity values, while Y is a non-metal element and generally has high electronegativity values. In this case, since X is a metal element and Y is a non-metal element, we can predict that the bond between them will be an electrovalent or ionic bond. An electrovalent bond is formed when electrons are transferred from a metal to a non-metal element. The metal element becomes positively charged and the non-metal element becomes negatively charged, forming ions. The attraction between the oppositely charged ions forms the electrovalent bond. Therefore, the type of bond that exists between element X with atomic number 12 and Y with atomic number 17 is electrovalent or ionic. Note: The term "electrovalent" is an older term for ionic bonds, which is why the option uses this term.

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Baking powder is a leavening agent used in baking that helps the dough to rise by releasing carbon dioxide gas when it reacts with moisture and heat. The main constituents of baking powder are baking soda (sodium bicarbonate) and an acid (usually cream of tartar). When these two ingredients are mixed with a small amount of cornstarch to prevent clumping, it forms baking powder. When baking powder is added to the dough, the baking soda and acid react with each other in the presence of moisture and heat. This reaction produces carbon dioxide gas, which gets trapped in the dough and causes it to rise. Therefore, the correct option from the given list is NaHCO3, which is baking soda (sodium bicarbonate), the primary ingredient responsible for making the dough rise in baking powder.

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The diagram shows a decrease in the rate of reaction over time. The most likely explanation for this effect is a decrease in the concentration of the reactants. This is because a lower concentration means that there are fewer reactant molecules available to collide and react with each other, resulting in a slower rate of reaction. Decreases in temperature, surface area, or pressure can also affect the rate of reaction, but these factors are not as clearly illustrated by the diagram. A decrease in temperature would cause the reaction to slow down, but the effect would be gradual rather than sudden. A decrease in surface area would also slow down the reaction, but it would not necessarily cause a sudden drop in the rate of reaction. A decrease in pressure might speed up the reaction if the reactants are in the gas phase, but again, the effect would not be as clearly illustrated by the diagram.

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The arrangement of particles in crystal lattices can be studied using X-rays. X-rays have a very short wavelength, which allows them to diffract when they pass through a crystal lattice. The diffraction pattern created by the X-rays provides information about the spacing and arrangement of the atoms in the crystal. By analyzing the diffraction pattern, scientists can determine the crystal structure and the positions of the atoms within the lattice. Gamma rays, alpha rays, and beta rays are not typically used to study crystal structures, as they have different properties and are not well-suited for this purpose.

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Among the options listed, the noble gas commonly found in the atmosphere is Argon. Argon makes up approximately 0.9% of the Earth's atmosphere and is the third most abundant gas after nitrogen and oxygen. Neon and helium are also noble gases, but they are not commonly found in the atmosphere because they are both lighter than air and tend to escape to the upper atmosphere. Xenon, on the other hand, is a rare gas and only exists in trace amounts in the atmosphere.

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A chemical reaction in which the hydration energy is greater than the lattice energy is referred to as an exothermic reaction. This means that the energy released during the formation of new chemical bonds is greater than the energy required to break the existing bonds. The excess energy is released into the surroundings in the form of heat, causing the reaction to feel warm. This type of reaction typically occurs spontaneously and does not require external energy input to proceed. An example of an exothermic reaction is the combustion of fuels such as gasoline or natural gas, which release heat and energy as they react with oxygen.

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Fehling's solution is a chemical test used to distinguish between reducing sugars (which have a free aldehyde or ketone group) and non-reducing sugars (which do not have a free aldehyde or ketone group). When a reducing sugar is added to Fehling's solution and heated, it reduces the copper(II) ions in the solution to form a brick-red precipitate of copper(I) oxide. In this case, compound K formed a brick-red precipitate when treated with Fehling's solution, indicating that it is a reducing sugar or a compound that contains a free aldehyde or ketone group. On the other hand, compound L remained unaffected, indicating that it is not a reducing sugar and does not contain a free aldehyde or ketone group. Among the given options, the only compound that contains a free aldehyde or ketone group is an alkanal. Therefore, the compound K is an alkanal.

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Corrosion is a process that occurs when a metal is exposed to its environment, and it results in the gradual destruction or deterioration of the metal. The condition required for corrosion to take place is the presence of water and oxygen. The presence of carbon (IV) oxide may also contribute to the process, but it is not necessary for corrosion to occur. When metal is exposed to air and moisture, a chemical reaction occurs between the metal and the oxygen in the air, which produces metal oxide. This metal oxide is what causes the corrosion of the metal.

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To find the concentration of a solution, we need to calculate the number of moles of solute (NaOH) in 100 cm³ of solution. First, we need to find the molar mass of NaOH: Na = 23 g/mol, O = 16 g/mol, H = 1 g/mol, so the molar mass of NaOH is 23 + 16 + 1 = 40 g/mol. We are given that there are 2 g of NaOH in the solution, so the number of moles of NaOH is: 2 g ÷ 40 g/mol = 0.05 mol Now we can calculate the concentration: Concentration = Number of moles ÷ Volume of solution Concentration = 0.05 mol ÷ 0.1 dm³ = 0.5 mol/dm³ So the concentration of the solution is 0.50 mol/dm³. Therefore, the correct option is: - 0.50 mol dm⁻³

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In the given chemical reaction, CH3COOH reacts with OH- to form CH3COO- and H2O. The compound CH3COOH is an acid because it donates a proton (H+) to the OH- ion, which accepts the proton to form H2O. As a result, CH3COO- is formed, which is the conjugate base of CH3COOH. So, the answer is "conjugate base."

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The ability of carbon to form long chains is referred to as catenation. Catenation is the property of an element to form a long chain or branch of atoms by bonding covalently with other atoms of the same element. Carbon is known for its strong catenation property due to its tetravalency (ability to form four covalent bonds) and small atomic size. This property of carbon allows it to form a variety of organic compounds, including hydrocarbons and polymers, which are the building blocks of life. Therefore, the correct answer is "catenation."

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The given chemical equation shows a reversible reaction where nitrogen dioxide (NO2) and dinitrogen oxide (N2O4) are in equilibrium. The reaction is endothermic, which means it absorbs heat. According to Le Chatelier's principle, an increase in temperature will favor the endothermic reaction, which absorbs heat. As a result, the equilibrium will shift in the direction that consumes heat, which in this case is the forward reaction. Therefore, an increase in temperature will shift the equilibrium to the right, favoring the formation of more NO2 gas and reducing the concentration of N2O4. As a result, the equilibrium constant (K) for this reaction, which is the ratio of products to reactants at equilibrium, will increase. Thus, the correct answer is "increase the value of the equilibrium constant."

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The given chemical reaction involves the formation of an ester from a carboxylic acid (CH3COOH) and an alcohol (C2H5OH) in the presence of a catalyst (H2SO4). This process is known as esterification. Therefore, the correct option is: Esterification.

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The principle of column chromatography is based on the ability of the constituents to move at different speeds in the column. In column chromatography, a mixture is passed through a column containing a stationary phase (e.g. silica gel) and a mobile phase (e.g. solvent). Different constituents of the mixture have different affinities for the stationary and mobile phases, and thus move at different speeds through the column. This allows them to be separated based on their different physical and chemical properties.

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Bronze is preferred to copper in the making of medals because it is stronger. Bronze is an alloy made up of copper and tin, which increases its strength compared to pure copper. This increased strength allows for more intricate designs to be made on the medal without the risk of the medal breaking or becoming distorted. Additionally, bronze has a distinct color that is often associated with medals, making it a popular choice for commemorative or decorative items. The other options mentioned in the question, such as low-temperature resistance or lightness, are not relevant factors in the preference for bronze over copper in medal-making.

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Thermal pollution refers to the sudden increase or decrease in the temperature of water bodies due to human activities. An effect of thermal pollution on water bodies is that the level of oxygen reduces. This happens because warm water cannot hold as much oxygen as cooler water, so as the temperature rises, the amount of oxygen in the water decreases. This can lead to a decrease in the number of fish and other aquatic organisms that require oxygen to survive. Additionally, thermal pollution can also cause changes in the ecosystem and affect the balance of aquatic life.

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Polymerization is a chemical reaction that involves the combination of many small molecules to form a large molecule with repeating structural units, called a polymer. In order for a compound to undergo polymerization, it should have a monomer or multiple monomers that can form a repeating pattern. Looking at the options given, compound (C2H4)n, also known as polyethylene, is a polymer and can undergo polymerization reaction. This is because its monomer, ethylene, contains a double bond that can break and form a chain of repeating units. On the other hand, compounds (C2H5COOH), (C2H6), and (C2H5OH) are not likely to undergo polymerization reaction because they do not have functional groups that can easily form repeating units. Therefore, the compound that will undergo polymerization reaction is (C2H4)n.

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The given equation represents the process of fermentation, in which glucose (C6H12O6) is converted into ethanol (C2H5OH) and carbon dioxide (CO2), with the help of the enzyme zymase. Therefore, the correct answer is ethanol.

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The presence of impurities such as carbon and sulphur in iron will lower its melting point. This is because impurities disrupt the regular arrangement of iron atoms, making it more difficult for them to move and reducing the amount of heat energy required for the iron to change from a solid to a liquid state. As a result, the melting point of the iron is decreased, making it easier to melt. It is important to note that while impurities may affect other properties of iron, such as its tensile strength or ductility, the question specifically asks about their effect on the melting point.

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The relative atomic mass of an element is the average mass of all the isotopes of that element, taking into account their natural abundance. Lithium has two naturally occurring isotopes: lithium-6 and lithium-7. The first isotope, lithium-6, makes up 90% of naturally occurring lithium, while the second isotope, lithium-7, makes up the remaining 10%. To find the relative atomic mass of this mixture of isotopes, we need to take the weighted average of their atomic masses, where the weights are their natural abundances. The atomic mass of lithium-6 is 6 atomic mass units (amu), while the atomic mass of lithium-7 is 7 amu. Using the formula for weighted average, we get: (0.9 x 6 amu) + (0.1 x 7 amu) = 5.4 amu + 0.7 amu = 6.1 amu Therefore, the relative atomic mass of naturally occurring lithium consisting of 90% Li-6 and 10% Li-7 is 6.1 amu, which is closest to option (C) 6.2.