Ch 3 – Exercise 8

NUMERICAL PROBLEMS USING CHEMICAL EQUATIONS

Ch 3 – Exercise 81. Calcium carbonate is decomposed during heating.

CaCO3 → CaO + CO2

25 g of calcium carbonate is heated until reaction is complete?(a) What is the mass of carbon dioxide produced?(b) What is the volume of carbon dioxide produced?[Relative atomic mass of Ca = 40; C = 12; O = 16; Molar volume of gas at room conditions is 24 dm3]

2. Magnesium carbonate is decomposed during heating.

MgCO3 → MgO + CO2

What is the mass of magnesium carbonate required to produce 560 cm3 of carbon dioxide gas at STP?[Relative atomic mass of Mg = 24; C = 12; O = 16; Molar volume of gas at STP is 22.4 dm3]

3. Decomposition of sodium nitrate by heat is shown by the equation. 2NaNO3 → 2NaNO2 + O2

How many moles of oxygen is liberated when 8.5 g of sodium nitrate decomposed completely?[Relative atomic mass of Na = 23; N = 14; O = 16]

4. The reaction between magnesium and sulphur dioxide is represented by the equation below:2Mg + SO2 → 2MgO + SWhat is the mass of magnesium oxide obtained when 40.0 g of sulphur dioxide reacts with excess magnesium?

[Relative atomic mass of Mg = 24; S = 32; O = 16]

5. ZnCO3 + 2HCl → ZnCl2 + H2O + CO2

In the above reaction, how many moles of hydrochloric acid is react completely with 6.25 g of zinc carbonate?[Relative atomic mass of Zn = 65; C = 12; O =16]

6. 2H2O2(aq) → 2H2O(l) + O2(g)In the above reaction, what is the mass of hydrogen peroxide, H2O2 required to produce 1.2 x 1023 molecules of oxygen gas?[Relative atomic mass of H = 1; O = 16; Avogadro Constant = 6 x 1023 mol-1]

Answers1. 11g; 6 dm3 2. 2.1 g 3. 0.05 mol4. 50 g 5. 0.1 mol 6. 13.6 g