Question

If the decomposition of a sample of KClO3 produces 3.29 g of O2. What was the mass (g) of the original sample?

Answer 1

Answer: 8.41 g

Step-by-step explanation:

To calculate the moles :

`\text{Moles of solute}=\frac{\text{given mass}}{\text{Molar Mass}}`

`\text{Moles of} O_2=(3.29g)/(32g/mol)=0.103moles`

The balanced chemical equation for decomposition is :

`2KClO_3\rightarrow 2KCl+3O_2`

According to stoichiometry :

As 3 moles of
`O_2` are produced by = 2 moles of
`KClO_3`

Thus 0.103 moles of
`O_2` are produced by =
`(2)/(3)* 0.103=0.0687moles` of
`KClO_3`

Mass of
`KClO_3=moles* {\text {Molar mass}}=0.0687moles* 122.5g/mol=8.41g`

8.41 g was the mass of the original sample.