Chemical Reactions: Displacement, Oxidation, and Conservation of Mass

Part A

DD, D, S, SD, D, S, D, SD, S, DD

Part B

Cu(NO₃)₂ + Ag: No reaction
MgCl₂ + H₂: No reaction
SnSO₄ + H₂: No reaction
Na₂O + Cu: No reaction

Part C

Part C(a, i)

Zinc + Lead(II) nitrate → Zinc nitrate + Lead

(ii) Zn + Pb(NO₃)₂ → Zn(NO₃)₂ + Pb

(iii) Zn + Pb(NO₃)₂ → Zn(NO₃)₂ + Pb

Part C(b)

Hydrogen + Nitrogen monoxide → Water + Nitrogen gas

(ii) H₂ + NO → H₂O + N₂

(iii) 2H₂ + 2NO → 2H₂O + N₂

Part C(c)

Hydrogen peroxide → Water + Oxygen gas

(ii) H₂O₂ → H₂O + O₂

(iii) 2H₂O₂ → 2H₂O + O₂

Part C(d)

Aluminium + Iron(III) oxide → Iron + Aluminium oxide

(ii) Al + Fe₂O₃ → Fe + Al₂O₃

(iii) 2Al + Fe₂O₃ → 2Fe + Al₂O₃

Part D

A single displacement reaction occurs when one element replaces another element in a compound. Example: Zn + Pb(NO₃)₂ → Zn(NO₃)₂ + Pb

A double displacement reaction occurs when two compounds exchange ions to form two new compounds. Example: AgNO₃ + NaCl → AgCl + NaNO₃

Compare: Both reactions produce new substances, but a single displacement reaction involves one element replacing another, while a double displacement reaction involves two compounds exchanging ions.

Part D(2): Evidence of a Chemical Reaction

• Colour change: A new colour appears, showing that a new substance may have been formed.
• Gas production: Bubbles form, showing that a gas may have been released.
• Change in odour: A new smell is produced.

Part E

Part E(1.a)

Magnesium oxide: MgO

Part E(1.b)

Mg + O₂ → MgO and 2Mg + O₂ → 2MgO

Part E(1.c)

40 - 24 = 16 g of oxygen. This shows the law of conservation of mass.

Part E(2)

Magnesium oxide; Potassium + Oxygen gas; No reaction; Potassium nitrate + Lead(II) iodide

Part E(3)

Reactants: Ethane + Oxygen
Products: Carbon monoxide + Carbon + Water

Part F

Part F(A)

Chlorinating agents

Part F(B)

They release chlorine, which kills bacteria and other harmful organisms in the water.

Part F(C)

Pool chemicals can react dangerously when mixed with the wrong chemicals, which can cause an explosion. They can also be corrosive and cause chemical burns if they come into contact with skin.

Part F(2)

A precipitation reaction would be best because it will form a solid and help remove the arsenate ions from the water.

Part F(3)

The atoms rearrange to form new substances. The bonds between the atoms break and new bonds form. Atoms are not created or destroyed, so the same number of each type of atom is present.