CIE iGCSE Co-Ordinated Science C4.2 Hydrogen–oxygen fuel cells Exam Style Questions Paper 1
▶️ Answer/Explanation
The cathode is the negative electrode, where positive ions gain electrons in a reduction reaction.
In dilute sulfuric acid, the positive ions present are hydrogen ions, \( \text{H}^+ \), which are reduced to form hydrogen gas at the cathode.
Oxygen forms at the anode instead, and sulfur dioxide and water vapour are not products of this electrolysis.
✅ Answer: (A)
In dilute sulfuric acid, the positive ions present are hydrogen ions, \( \text{H}^+ \), which are reduced to form hydrogen gas at the cathode.
Oxygen forms at the anode instead, and sulfur dioxide and water vapour are not products of this electrolysis.
✅ Answer: (A)
▶️ Answer/Explanation
Structure 1 (ethanol) has the molecular formula \(\text{C}_2\text{H}_6\text{O}\), matching the two carbons, six hydrogens and one oxygen shown.
Structure 3 (nitric acid) has the formula \(\text{HNO}_3\), matching one hydrogen, one nitrogen and three oxygens; structure 2 should be \(\text{CO}_2\) and structure 4 should be \(\text{SO}_2\), not the formulas given.
✅ Answer: (B)
Structure 3 (nitric acid) has the formula \(\text{HNO}_3\), matching one hydrogen, one nitrogen and three oxygens; structure 2 should be \(\text{CO}_2\) and structure 4 should be \(\text{SO}_2\), not the formulas given.
✅ Answer: (B)
▶️ Answer/Explanation
The electrode connected to the positive terminal of the supply is the anode, and the one connected to the negative terminal is the cathode.
For copper chloride to conduct and undergo electrolysis, it must be in the aqueous (dissolved) state, not solid.
So labels 1, 2 and 3 correspond to anode, cathode and aqueous respectively.
✅ Answer: (A)
For copper chloride to conduct and undergo electrolysis, it must be in the aqueous (dissolved) state, not solid.
So labels 1, 2 and 3 correspond to anode, cathode and aqueous respectively.
✅ Answer: (A)
▶️ Answer/Explanation
The limewater turning cloudy confirms carbon dioxide gas is produced, showing carbon has removed oxygen from the metal oxide.
Loss of oxygen from a compound is defined as reduction.
The metal oxide is therefore reduced to the free metal while the carbon is oxidised to carbon dioxide.
✅ Answer: (D)
Loss of oxygen from a compound is defined as reduction.
The metal oxide is therefore reduced to the free metal while the carbon is oxidised to carbon dioxide.
✅ Answer: (D)
▶️ Answer/Explanation
Sodium chloride is an ionic compound that can be split into its elements by electrolysis.
Passing an electric current through molten sodium chloride produces sodium at the cathode and chlorine at the anode.
✅ Answer: (D)
Passing an electric current through molten sodium chloride produces sodium at the cathode and chlorine at the anode.
✅ Answer: (D)