Question

# $$4.90$$ g of $$KClO_3$$, on heating shows a weight loss of $$0.384g$$. What percentage of the original $$KClO_3$$ has decomposed?

Solution

## $$2KClO_{3} + heat \rightarrow 2KCl + 3O_{2}$$2mol $$KClO_{3}$$ produce 3 mol $$O_2$$The 0.384 g mass loss was due to the oxygen generated.The amount of moles of oxygen generated can be calculated as: Molar mass $$O_2$$ = 32 g/mol0.384 g $$O_2$$ = 0.384/32 = 0.012 mol $$O_2$$ generatedThis came from the decomposition of 0.012 x 2/3 = 0.008 mol of$$KClO_3$$Molar mass $$KClO_3$$  = 122.55 g/mol 0.008 mol $$KClO_3$$ = 0.008 x 122.55 = 0.9804 g $$KClO_3$$ decomposed% of original sample$$=\dfrac{0.9804}{4.90}\times 100=20\%$$Chemistry

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