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Question 1 Report
A WEAK ACID IS ONE WHICH
Answer Details
A weak acid is one which is slightly ionized in water. In other words, when a weak acid is dissolved in water, only a small fraction of its molecules dissociate into ions. This is in contrast to a strong acid, which dissociates almost completely into ions when dissolved in water. As a result of its weak ionization, a weak acid has a lower acidity compared to a strong acid.
Question 2 Report
What is the percentage by mass of copper in copper in copper (l) oxide (CU2O)? [O = 16; CU =64]
Answer Details
To determine the percentage by mass of copper in copper (I) oxide (Cu2O), we need to calculate the molar mass of Cu2O, which is the sum of the atomic masses of the elements in the compound. Molar mass of Cu2O = 2Cu + O = (2 x 64) + 16 = 144 g/mol The molar mass of copper in Cu2O is 2 x 64 = 128 g/mol The percentage by mass of copper in Cu2O is: (128 g Cu / 144 g Cu2O) x 100% = 88.9% Therefore, the correct answer is 88.9%.
Question 3 Report
Which of the following is an alloy of mercury?
Answer Details
The alloy of mercury is amalgam. An amalgam is a type of alloy that consists of mercury as one of the components. Amalgams are usually used in dentistry to fill cavities. When mercury is mixed with other metals like silver, tin, or copper, it forms a soft, pliable material that can be easily shaped to fill the cavity. Once the amalgam hardens, it becomes a durable and long-lasting filling. Therefore, the correct answer is Amalgam.
Question 4 Report
In which of the following processes are larger molecules broken down into smaller molecules?
Answer Details
The process in which larger molecules are broken down into smaller molecules is called "degradation" or "cracking". Out of the given options, the process that involves larger molecules being broken down into smaller molecules is "hydrolysis of starch". Hydrolysis is a chemical reaction that involves the breaking of a bond in a molecule using water. In the case of starch, it is broken down into smaller glucose molecules by the addition of water molecules, resulting in a simpler and smaller molecule. The other processes listed involve the formation or combination of molecules rather than their breakdown.
Question 6 Report
The gas produced when a mixture of sodium propanoate and soda lime is heated is
Answer Details
Question 7 Report
Which of the following is not correct of the reaction represented by the equation below? 2C(s) + O2(g) → 2CO(g); ∆H = - xKJ
Question 8 Report
A positive brown ring test indicates the presence of
Answer Details
The positive brown ring test indicates the presence of nitrate ions (NO3). The test is done by adding freshly prepared iron(II) sulfate (FeSO4) solution and concentrated sulfuric acid (H2SO4) to the test solution. If nitrate ions are present in the solution, a brown ring will form at the junction of the two liquids. This occurs because nitrate ions reduce Fe2+ ions to Fe3+ ions, which then react with the sulfuric acid to form Fe(HSO4)2 which appears as the brown ring.
Question 9 Report
What is the amount (in mole) of hydrogen gas that would be produced if 0.6 mole of hydrochloric acid reacted with excess zinc according to the following equation? Zn(s) + 2HCI(aq) → ZnCI2(aq) + H2(g)
Answer Details
According to the balanced chemical equation, 1 mole of zinc reacts with 2 moles of hydrochloric acid to produce 1 mole of hydrogen gas. Zn(s) + 2HCI(aq) → ZnCI2(aq) + H2(g) Therefore, if 0.6 mole of hydrochloric acid is used, it will react with 0.3 mole of zinc to produce 0.3 mole of hydrogen gas. Thus, the amount of hydrogen gas produced is 0.3 mole. Therefore, the correct option is: 0.3 mole.
Question 10 Report
What mass of copper will be deposited by the liberation of Cu2+ when 0.1F of electricity flows through an aqueous solution of a copper (ll) salt? [Cu = 64]
Answer Details
Question 12 Report
Which of the following is hydrocarbons is unsaturated?
Answer Details
The hydrocarbon that is unsaturated is benzene. A hydrocarbon is considered unsaturated when it contains at least one double or triple bond between carbon atoms, which means that it has fewer hydrogen atoms per carbon atom than a saturated hydrocarbon. Benzene is an unsaturated hydrocarbon with a ring structure and alternating double bonds between carbon atoms. The other options, ethane, propane, 2-methylbutane, and 2,2,4-trimethylpentane, are all saturated hydrocarbons, which means they only have single bonds between carbon atoms and are fully saturated with hydrogen atoms.
Question 14 Report
The following alkanols will yield alkanoic acids on reacting with excess acidified K2Cr2O7 except
Answer Details
The alkanols that will yield alkanoic acids on reacting with excess acidified K2Cr2O7 are primary and secondary alkanols. Tertiary alkanols do not undergo oxidation. Therefore, the correct answer is (CH3)3COH, which is a tertiary alcohol and cannot be oxidized to an alkanoic acid.
Question 15 Report
Consider the reaction represented by the equation below: XO + YO → X + YO2 In the reaction, YO acts as
Answer Details
In the given chemical equation, XO is being reduced, and YO is being oxidized. An oxidizing agent is a substance that causes another substance to be oxidized, while a reducing agent is a substance that causes another substance to be reduced. YO is being reduced, which means it is causing the reduction of XO. Thus, YO is acting as a reducing agent.
Question 16 Report
Which of the following cannot be deduced from the electronic configuration of a transition metal?
Answer Details
Question 17 Report
The following salts dissolve readily in cold water except
Answer Details
Among the given options, the salt that does not dissolve readily in cold water is PbSO4. This is because PbSO4 is an ionic compound with a high lattice energy, meaning that its ions are held together by strong electrostatic forces of attraction. These forces of attraction make it difficult for the PbSO4 crystals to break apart and dissolve in water. Therefore, PbSO4 is considered insoluble in water. The other options, such as CaCI2, (NH4)2SO4, Na2CO3, and Na2SO3, readily dissolve in cold water due to their ionic nature and low lattice energy.
Question 18 Report
Copper (ll) tetraoxosulphate (VI) is often added to swimming pools because it
Answer Details
Copper (II) tetraoxosulphate (VI) is often added to swimming pools because it prevents the growth of algae. Algae can grow in the warm, moist environment of swimming pools and can make the water appear green and murky. Copper (II) tetraoxosulphate (VI) is a powerful algicide that can prevent the growth of algae in swimming pools. When added to the water, it releases copper ions which are toxic to algae and prevent their growth. Copper (II) tetraoxosulphate (VI) is a safe and effective way to keep swimming pools clean and clear.
Question 19 Report
The function of limestone in the extraction of iron in the blast furnace is
Answer Details
The function of limestone in the extraction of iron in the blast furnace is to remove impurities from the iron ore. During the extraction process, iron ore is heated with coke (a form of carbon) and air to produce molten iron, which is then drained from the bottom of the furnace. However, the iron ore contains impurities such as silicon dioxide (SiO2), which is acidic in nature and can corrode the lining of the furnace. Limestone (calcium carbonate, CaCO3) is added to the blast furnace to act as a flux, which neutralizes the acidic impurities and forms a slag, a waste material that can be easily removed from the furnace. Thus, the function of limestone is to purify the iron ore by removing the impurities and prevent the corrosion of the furnace lining.
Question 20 Report
If a solid has a low melting point and dissolves readily in benzene, it would probably
Answer Details
If a solid has a low melting point and dissolves readily in benzene, it would probably have covalent bonding. Covalent compounds are those that are held together by sharing of electrons between atoms, and they typically have low melting points and do not conduct electricity in either the solid or molten state. Benzene, a nonpolar solvent, readily dissolves covalent compounds, which explains why the solid in question dissolves readily in it. Strong electrostatic forces of attraction are associated with ionic compounds, which typically have high melting points and are soluble in polar solvents like water.
Question 21 Report
The following can be obtained directly from the destructive distillation of coal except
Answer Details
Destructive distillation is the process of heating coal in the absence of air to obtain useful products. During this process, coal is broken down into various components. Ammoniacal liquor, coal gas, coke, and coal tar are some of the products obtained from the destructive distillation of coal. However, producer gas is not obtained directly from the destructive distillation of coal. It is obtained by passing air over coke at a high temperature. Therefore, the correct option is "producer gas."
Question 22 Report
H3O+(aq) + OH-(aq) → 2H2O(l). The heat change accompanying the process represented by the equation above is the heat of
Answer Details
The heat change accompanying the given process is the heat of neutralization. This is because the reaction involves the combination of hydrogen ions (H+) from an acid (represented by the H3O+ ion) and hydroxide ions (OH-) from a base to form water molecules (H2O). This process of combining an acid and a base to form a salt and water is called neutralization. The heat released or absorbed during this process is known as the heat of neutralization.
Question 23 Report
Which of the following molecules is linear in shape?
Answer Details
The shape of a molecule is determined by its electronic geometry, which depends on the arrangement of the atoms and the number of electron pairs around the central atom. A molecule is considered linear if it has two atoms and no lone pairs of electrons on the central atom. Based on this definition, the molecule that is linear in shape is CI2 because it has two chlorine atoms and no lone pairs of electrons on the central atom. All the other molecules listed have lone pairs or more than two atoms, which means they are not linear in shape.
Question 24 Report
Sodium chloride cannot conduct electricity in the solid state because it
Answer Details
Sodium chloride (NaCl) cannot conduct electricity in the solid state because it does not contain mobile ions. In the solid state, the sodium (Na) and chloride (Cl) ions are held tightly in a lattice structure, and cannot move freely to conduct an electric current. When dissolved in water, NaCl dissociates into its ions, which are free to move and conduct electricity. Therefore, NaCl is an example of an ionic compound that conducts electricity only when dissolved in water or melted.
Question 25 Report
What is the amount (in mole) of hydrogen gas that would be produced if 0.6 mole of hydrochloric acid reacted with excess zinc according to the following equation? Zn(s) + 2HCI(aq) → ZnCI2(aq) + H2(g)
Answer Details
From the balanced chemical equation, it is observed that 1 mole of Zinc reacts with 2 moles of Hydrochloric acid to produce 1 mole of Hydrogen gas. Therefore, 0.6 mole of Hydrochloric acid would react with 0.3 mole of Zinc and produce 0.3 mole of Hydrogen gas. So the answer is (c) 0.3 mole.
Question 26 Report
What mass of copper will be deposited by the liberation of Cu2+ when 0.1F of electricity flows through an aqueous solution of a copper (ll) salt? [Cu = 64]
Answer Details
The amount of substance that is deposited during an electrolysis reaction can be calculated using Faraday's laws of electrolysis. According to Faraday's laws, the amount of substance deposited is directly proportional to the amount of electricity that flows through the solution. The formula that relates the amount of substance to the amount of electricity is: Amount of substance = (Electricity in Coulombs) / (Faraday constant x Valency) where the Faraday constant is the amount of electric charge per mole of electrons, and the valency is the number of electrons involved in the redox reaction. For the given problem, the copper (II) ion has a valency of 2, and we are given that 0.1 F of electricity flows through the solution. The Faraday constant is 96,485 Coulombs per mole of electrons. Therefore, the amount of copper that will be deposited can be calculated as: Amount of substance = (0.1 F) / (2 x 96,485 C/mol) = 5.18 x 10^-5 mol The molar mass of copper is 64 g/mol, so the mass of copper that will be deposited is: Mass of copper = Amount of substance x Molar mass = 5.18 x 10^-5 mol x 64 g/mol = 0.00331 g ≈ 3.2 g (rounded to one decimal place) Therefore, the answer is 3.2g.
Question 27 Report
Which of the following species is always present in acidified water?
Answer Details
The species that is always present in acidified water is H3O+. When water is mixed with an acid, it produces H+ ions, which react with water to form H3O+ ions. These ions are responsible for the acidic properties of the solution. Therefore, out of the given options, H3O+ is the correct choice.
Question 28 Report
The most suitable method for preparing lead (ll) chloride is by
Answer Details
The most suitable method for preparing lead (II) chloride is by mixing aqueous solutions of Pb(NO3)2 and NaCI. When aqueous solutions of lead nitrate and sodium chloride are mixed, a white precipitate of lead (II) chloride is formed. The other options mentioned in the question are not suitable for preparing lead (II) chloride. For example, the action of dilute HCl on PbSO4 will produce lead (II) sulfate, not lead (II) chloride. Similarly, the action of dilute HCl on lead will produce lead (II) chloride, but it is not the most suitable method for preparing lead (II) chloride. Therefore, the correct answer is "mixing aqueous solutions Pb(NO3)2 and NaCI."
Question 29 Report
Alums are classified as
Answer Details
Alums are classified as double salts. Double salts are compounds that contain two different cations and one anion, held together by ionic bonds. In the case of alums, they are double salts of a monovalent cation (such as potassium or ammonium), a trivalent cation (such as aluminum or chromium), and a sulfate anion. The general formula for alums is M^+M^3+(SO4)2·12H2O, where M^+ is a monovalent cation and M^3+ is a trivalent cation. Alums are commonly used as mordants in dyeing and in various industrial processes.
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