Chemistry — Reactions, Elements, Compounds

Question 1

Rusting of iron is:‌​‍

Accepted Answer

Oxidation — Rusting = oxidation of iron (Fe + O₂ + H₂O → Fe₂O₃).‌​‍

Answer

Reduction

Answer

Sublimation

Answer

Neutralisation

Question 2

The most abundant metal in Earth's crust is:‌​‍

Accepted Answer

Aluminium — Aluminium (~8%) is the most abundant metal. ‌​‍Oxygen (~46%) is the most abundant element overall.

Answer

Iron

Answer

Copper

Answer

Gold

Question 3

Acid + Base →‌​‍

Accepted Answer

Salt + Water — Neutralisation reaction: Acid + Base → Salt + Water.‌​‍

Answer

Salt + Gas

Answer

Water + Gas

Answer

Metal + Water

Question 4

The pH of lemon juice is approximately:‌​‍

Accepted Answer

2-3 — Lemon juice is acidic with pH ~2-3 (contains citric acid).‌​‍

Answer

7

Answer

9-10

Answer

14

Question 5

Which metal is stored in kerosene?‌​‍

Accepted Answer

Sodium — Sodium is highly reactive with air and water, so it's stored in kerosene to prevent reactions.‌​‍

Answer

Gold

Answer

Iron

Answer

Copper

Question 6

The gas produced when acid reacts with metal is:‌​‍

Accepted Answer

Hydrogen — Metal + Acid → Salt + Hydrogen gas. The 'pop' test confirms hydrogen.‌​‍

Answer

Oxygen

Answer

Nitrogen

Answer

Carbon Dioxide

Question 7

Plaster of Paris is:‌​‍

Accepted Answer

CaSO₄·½H₂O — Plaster of Paris = Calcium Sulphate Hemihydrate (CaSO₄·½H₂O). ‌​‍Used in casts and moulds.

Answer

CaCO₃

Answer

Ca(OH)₂

Answer

CaO

Question 8

Bleaching powder is:‌​‍

Accepted Answer

Ca(OCl)₂ — Bleaching powder = Calcium Hypochlorite Ca(OCl)₂. ‌​‍Used for water purification and bleaching.

Answer

NaOCl

Answer

NaHCO₃

Answer

CaCO₃

Question 9

The non-metal that is liquid at room temperature is:‌​‍

Accepted Answer

Bromine — Bromine is the only non-metal liquid at room temperature. ‌​‍Mercury is the only liquid metal.

Answer

Mercury

Answer

Iodine

Answer

Phosphorus

Question 10

Galvanisation is coating iron with:‌​‍

Accepted Answer

Zinc — Galvanisation = coating iron with zinc to prevent rusting.‌​‍

Answer

Copper

Answer

Tin

Answer

Chromium

Question 11

The gas responsible for global warming is:‌​‍

Accepted Answer

Carbon Dioxide — CO₂ is the primary greenhouse gas causing global warming through the greenhouse effect.‌​‍

Answer

Oxygen

Answer

Nitrogen

Answer

Helium

Question 12

Aqua regia is a mixture of:‌​‍

Accepted Answer

HCl + HNO₃ — Aqua regia (3:1 HCl:HNO₃) can dissolve gold and platinum — 'Royal Water'.‌​‍

Answer

H₂SO₄ + HCl

Answer

HNO₃ + H₂SO₄

Answer

HCl + CH₃COOH

Question 13

The gas used in welding is:‌​‍

Accepted Answer

Acetylene — Acetylene (C₂H₂) is used in oxy-acetylene welding due to its high flame temperature.‌​‍

Answer

Oxygen

Answer

Nitrogen

Answer

Hydrogen

Question 14

Washing soda formula is:‌​‍

Accepted Answer

Na₂CO₃ — Washing soda = Sodium Carbonate (Na₂CO₃·10H₂O). ‌​‍Used for cleaning and water softening.

Answer

NaCl

Answer

NaHCO₃

Answer

NaOH

Question 15

Vinegar contains:‌​‍

Accepted Answer

Acetic acid — Vinegar contains acetic acid (CH₃COOH). Lemon = citric acid. Stomach = HCl.‌​‍

Answer

HCl

Answer

Citric acid

Answer

Tartaric acid

Chemistry — Reactions, Elements, Compounds