12. Which of the following occur during the electrolysis of dilute H₂SO₄? A. The overall reaction is: H₂(g) + ½ O₂(g) → H₂O(g) B. SO₄²⁻ is discharged at the anode. C. A basic solution is formed. D. H⁺ is discharged at the negative electrode. 13. In an activity during laboratory session a small amount of lead bromide (PbBr₂) crystals were placed in a beaker. Two electrodes are inserted until they are in contact with the PbBr₂ crystals. When the PbBr₂ crystals in the beaker are gently heated, which of the following will be observed? A. Bromide ion is oxidized at the cathode. B. Bromine gas is evolved at the anode. C. Lead (II) ion is oxidized at the cathode. D. Lead (II) ion is reduced at the anode. 14. What is the name given to the pollution caused by the dumping of non-biodegradable wastes into the environment? A. Land pollution B. Air pollution C. Water pollution D. Sound pollution 15. What is the purpose of the conversion of pig iron to steel? A. To remove impurities by reduction. B. To remove impurities by oxidation. C. To decrease the concentration of iron in the pig iron. D. To increase the concentration of iron in the pig iron. 16. Which of the following statements CORRECTLY describes the law of conservation of mass? A. Mass is neither created nor destroyed during a chemical reaction. B. The total mass of substances varies during a chemical reaction. C. Pure compounds always contain the elements in the same percentage by mass. D. A particular compound is composed of the same elements in the same parts by mass.
Answer (1)
During the electrolysis of dilute H 2 SO 4 (sulfuric acid), the following occurs:
Option D: H⁺ is discharged at the negative electrode.
In electrolysis, positive ions (cations) move towards the negative electrode (cathode) to gain electrons. In this case, H + ions are discharged at the cathode, forming H 2 gas.
When lead bromide ( PbBr 2 ) is heated and electrolyzed:
Option B: Bromine gas is evolved at the anode.
At the anode (positive electrode), bromide ions ( Br − ) lose electrons (are oxidized) to form bromine gas ( Br 2 ).
Pollution caused by the dumping of non-biodegradable wastes into the environment is:
Option A: Land pollution.
Non-biodegradable waste that is improperly disposed of can accumulate on land, leading to environmental damage.
The purpose of converting pig iron to steel is:
Option B: To remove impurities by oxidation.
This process involves removing carbon and other impurities from pig iron primarily through oxidation, resulting in the production of more durable steel.
The statement that correctly describes the law of conservation of mass is:
Option A: Mass is neither created nor destroyed during a chemical reaction.
This principle states that in a closed system, the mass of the reactants equals the mass of the products, meaning total mass remains constant throughout a chemical reaction.
