Question
Calcium carbonate, CaCO3, reacts with dilute hydrochloric acid to produce carbon dioxide. The equation for the reaction is shown. The relative formula mass of calcium carbonate is 100.
\(CaCO_{3}+2HCl \rightarrow CaCl_{2}+H_{2}O+CO_{2}\)
10 g of calcium carbonate is reacted with an excess of dilute hydrochloric acid. Which mass of carbon dioxide is produced?
A. 2.2 g B. 2.8 g C. 4.4 g D. 44 g
▶️Answer/Explanation
Ans:
C
1o g CaCO3, has \(\frac{10 g}{100 g}\) = 0.1 mol
\(CaCO_{3}+2HCl \rightarrow CaCl_{2}+H_{2}O+CO_{2}\)
1 mol CaCO3 gives 1 mol CO2,
0.1 mol CaCO3 gives 0.1 mol CO2,
Mass of CO2, produced = 0.1*44 = 4.4 g.
Question
The equation for the reaction between magnesium and dilute sulfuric acid is shown.
\(Mg + H_2SO_4 → MgSO_4 + H_2\)
Mr of \(MgSO_4\) is 120
Which mass of magnesium sulfate will be formed if 12 g of magnesium are reacted with sulfuric acid?
A 5g B 10g C 60g D 120g
▶️Answer/Explanation
Ans: C
\(Mg + H_2SO_4 → MgSO_4 + H_2\)
1 mol Mg forms 1 mol \(MgSO_4\)
12 g of magnesium has \(\frac{12 g}{24 g}\) = 0.5 mol Mg
0.5 mol Mg will form 0.5 mol \(MgSO_4\)
Mr of \(MgSO_4\) is 120
0.5 mol \(MgSO_4\) will have mass of 0.5*120 = 60 g.
Question
The equation shows the thermal decomposition of magnesium carbonate (Mr = 84).
MgCO3 → MgO + CO2
Which mass of magnesium oxide is formed when 21.0 g of magnesium carbonate are completely decomposed?
A 1.9 g B 4.0 g C 10.0 g D 40.0 g
▶️Answer/Explanation
Ans: C
MgCO3 → MgO + CO2
1 mol MgCO3 produces 1 mol MgO
84 g MgCO3 produces 40 g MgO
1 g MgCO3 produces \(\frac{40 }{84 }\) g MgO
21 g MgCO3 produces \(\frac{21×40 }{84 }\) g MgO = 10 g MgO.