CIE iGCSE Co-Ordinated Science C3.3 The mole and the Avogadro constant Exam Style Questions Paper 1
▶️ Answer/Explanation
Lithium (Group I) forms an ion with a single positive charge: \( Li^+ \).
Bromine (Group VII) forms an ion with a single negative charge: \( Br^- \).
Since the charges are equal and opposite, they combine in a 1:1 ratio to give the formula LiBr.
✅ Answer: (A)
Bromine (Group VII) forms an ion with a single negative charge: \( Br^- \).
Since the charges are equal and opposite, they combine in a 1:1 ratio to give the formula LiBr.
✅ Answer: (A)
▶️ Answer/Explanation
The balanced equation is \( 2\text{HCl} + \text{Na}_2\text{CO}_3 \rightarrow 2\text{NaCl} + \text{CO}_2 + \text{H}_2\text{O} \).
Two HCl are needed to supply the two Na atoms as NaCl, giving \(w = 2\) and \(x = 2\).
One carbon dioxide and one water are produced, so \(y = 1\) and \(z = 1\).
✅ Answer: (D)
Two HCl are needed to supply the two Na atoms as NaCl, giving \(w = 2\) and \(x = 2\).
One carbon dioxide and one water are produced, so \(y = 1\) and \(z = 1\).
✅ Answer: (D)
▶️ Answer/Explanation
Sulfur dioxide is released when fossil fuels containing sulfur impurities are burned.
It is a recognised air pollutant that contributes to acid rain and respiratory problems.
Argon and nitrogen are unreactive natural components of air, and carbon dioxide is not classed as a pollutant in this context.
✅ Answer: (D)
It is a recognised air pollutant that contributes to acid rain and respiratory problems.
Argon and nitrogen are unreactive natural components of air, and carbon dioxide is not classed as a pollutant in this context.
✅ Answer: (D)
▶️ Answer/Explanation
The diagram shows the ratio of sodium, sulfur and oxygen atoms/ions present in the compound.
Counting the particles shown gives 2 sodium atoms, 1 sulfur atom and 4 oxygen atoms in the correct ratio for sodium sulfate.
Writing this ratio as a formula, with elements in the conventional order, gives \(Na_2SO_4\).
✅ Answer: (C)
Counting the particles shown gives 2 sodium atoms, 1 sulfur atom and 4 oxygen atoms in the correct ratio for sodium sulfate.
Writing this ratio as a formula, with elements in the conventional order, gives \(Na_2SO_4\).
✅ Answer: (C)
▶️ Answer/Explanation
A balanced equation must have equal numbers of each atom on both sides.
\( 2H_2 + O_2 \rightarrow 2H_2O \) gives 4 hydrogen atoms and 2 oxygen atoms on each side, so it is correctly balanced.
✅ Answer: (D)
\( 2H_2 + O_2 \rightarrow 2H_2O \) gives 4 hydrogen atoms and 2 oxygen atoms on each side, so it is correctly balanced.
✅ Answer: (D)