Asked in 24th Self Assessment TestModerate

In the absence of a catalyst, ammonia burns in an excess of oxygen to produce steam and nitrogen. What is the volume of oxygen remaining when 60 cm³ of ammonia is burnt in 100 cm³ of oxygen, all volumes being measured at the same temperature and pressure?

Correct answer: D. 55 cm³

  • A. 35 cm³
  • B. 40 cm³
  • C. 45 cm³
  • D. 55 cm³

Explanation

4NH3 + 3O2→ 6H2O + 2N2 60 cm³ 100 cm³ : Given (22,400 × 4) cm³ of ammonia uses (22,400 × 3) cm³ of O2 1 cm³ of ammonia uses .75 cm³ of O2 60 cm³ (given) of ammonia will use .75 × 60= 45 cm³ of O2 Hence the remaining volume of O2 will be 100-45=55 cm³

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About Limiting and Excess Reactants

Limiting and excess reactants are identified from the balanced chemical equation and the available amounts of each substance. The limiting reactant determines the maximum product formed, while the excess reactant remains after completion, so questions require mole ratios, theoretical yield and sometimes percentage yield calculations.

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