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ICSE Class 10 Chemistry Question 3 of 28

Stoichiometry — Percentage Composition — Empirical & Molecular Formula — Chemical Equations — Question 10

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Question 10

Sulphur burns in oxygen to give sulphur dioxide. If 16 g. of sulphur burns in 'x' cc. of oxygen, calculate the amount of potassium nitrate which must be heated to produce 'x' cc. of oxygen. [S = 32, K = 39, N = 14, O = 16].

Answer

2KNO3⟶2KNO2+O22[39+142×16+(16×3)]=32 g=202 g\begin{matrix} 2\text{KNO}_3 & \longrightarrow & 2\text{KNO}_2 & + & \text{O}_2 \\ 2[39 + 14 & & & & 2 \times 16 \\ + (16 \times 3)] & & & & = 32 \text{ g} \\ = 202 \text{ g} & & & & \end{matrix}

S+O2⟶SO232g\begin{matrix} \text{S} & + & \text{O}_2 & \longrightarrow & \text{SO}_2 \\ 32 \text {g} \\ \end{matrix}

32 g of sulphur require 202 g of potassium nitrate to be heated

∴ 16 g of sulphur will require 20232\dfrac{202}{32} x 16 = 101 g of potassium nitrate.

Hence, amount of potassium nitrate which must be heated is 101 g