QUARTER FINAL STAGE 2014
Opoku Ware SHS
Keta SHS
St Peter's SHS
ROUND 4 - TRUE OR FALSE
1. During rusting of iron, the iron metal is oxidized initially to iron(II).
ANSWER: TRUE
EXPLANATION:
$Fe \to Fe^{2+}$ initially, later further oxidized (with $O_2$/$H_2O$) toward the iron(III) oxide/hydroxide that makes up rust.
2. During rusting of iron, the iron metal is oxidized only in moist air.
ANSWER: TRUE
EXPLANATION:
Rusting requires both oxygen and water; dry air alone does not rust iron appreciably.
---
PRACTICE QUESTIONS
1. QUESTION: Painting iron prevents rusting by keeping out air and water.
ANSWER: TRUE
EXPLANATION:
Rusting needs both oxygen and water; the paint layer keeps them away from the iron.
2. QUESTION: Rust is mainly anhydrous iron(II) oxide.
ANSWER: FALSE
EXPLANATION:
Rust is hydrated iron(III) oxide, $Fe_2O_3\cdot xH_2O$.
3. QUESTION: Salt water speeds up rusting.
ANSWER: TRUE
EXPLANATION:
Dissolved ions make the water a better electrolyte, so the redox reactions go faster.
4. QUESTION: Galvanising protects iron from rusting by coating it with zinc.
ANSWER: TRUE
EXPLANATION:
Zinc is more reactive and corrodes in preference to the iron (sacrificial protection).
5. QUESTION: Rusting is the reduction of iron.
ANSWER: FALSE
EXPLANATION:
Iron loses electrons, so rusting is an oxidation.
6. QUESTION: Stainless steel rusts faster than ordinary iron.
ANSWER: FALSE
EXPLANATION:
The chromium in stainless steel forms a protective oxide layer.