Question 6

6.1 In an experiment, a learner added 1,5 g of sodium carbonate (Na2CO3) to
hydrochloric acid (HCℓ). A volume of 306 cm3 of carbon dioxide gas was
formed and collected under standard pressure at room temperature. Take the
molar gas volume at room temperature (Vm) as 24,45 dm3.

The unbalanced equation for the reaction is:

Na2CO3(s) + HCℓ(aq) → NaCℓ(aq) + H2O(ℓ) + CO2(g)

6.1.1 Define the term one mole of a substance. (2)

6.1.2 Balance the equation for the reaction. (2)

6.1.3 Calculate the mass of sodium carbonate that reacted. (7)

6.1.4 Calculate the percentage of sodium carbonate in excess. (2)

6.2 Zinc reacts with sulphuric acid according to the reaction below.

Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)

The mass of zinc is recorded during the experiment and is shown on the
graph below. The reaction stops after 2 minutes.

6.2.1 Name the substance that is the limiting reagent. (1)

6.2.2 Calculate the initial concentration of the sulphuric acid if 50 cm3 of
the acid was used. (5)



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