CIE iGCSE Co-Ordinated Science C7.1 The characteristic properties of acids and bases Exam Style Questions Paper 1
▶️ Answer/Explanation
An increase in pH indicates the solution is becoming more alkaline. Potassium (K) reacts with water to form potassium hydroxide (KOH), an alkali, which would increase the pH. HCl and SO₂ are acidic and would decrease the pH, while NaCl is a neutral salt and would not significantly change the pH.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
Acids react with carbonates (e.g. \(\mathrm{CaCO_3}\)) to produce a salt, water, and carbon dioxide gas. Alkalis and bases produce only salt and water (neutralisation). Metals react with acids to produce salt and hydrogen gas, but no water.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
Ammonia is a basic gas that reacts with acids; concentrated hydrochloric acid reacts with ammonia to produce dense white fumes of ammonium chloride: \(\text{NH}_3 + \text{HCl} \rightarrow \text{NH}_4\text{Cl}\).
This white smoke test is used to confirm the presence of ammonia gas; other options in the table (like sodium hydroxide solution or water) do not produce this characteristic white smoke.
✅ Answer: (B)
This white smoke test is used to confirm the presence of ammonia gas; other options in the table (like sodium hydroxide solution or water) do not produce this characteristic white smoke.
✅ Answer: (B)
▶️ Answer/Explanation
Acidic waste starts with a pH below 7.
Limestone is a base (calcium carbonate) that neutralises the acid in the waste.
After treatment, the pH rises towards 7, so the correct row shows a low pH before and a higher, closer-to-neutral pH after.
✅ Answer: (B)
Limestone is a base (calcium carbonate) that neutralises the acid in the waste.
After treatment, the pH rises towards 7, so the correct row shows a low pH before and a higher, closer-to-neutral pH after.
✅ Answer: (B)
▶️ Answer/Explanation
A pH of 10 indicates that the oxide’s solution is alkaline (basic), which is typical of metal oxides.
Magnesium is a reactive metal that burns in air to form magnesium oxide, a basic oxide.
Carbon and phosphorus are non-metals whose oxides are acidic, and argon does not react at all.
✅ Answer: (C)
Magnesium is a reactive metal that burns in air to form magnesium oxide, a basic oxide.
Carbon and phosphorus are non-metals whose oxides are acidic, and argon does not react at all.
✅ Answer: (C)