Question

Which of the following ratios are needed to determine the mass of oxygen produced from the decomposition of 10 grams of potassium chlorate? Select all that apply.

Answer 1

1 mole KClO3 / 122.55 g KClO3,

3 mole O2 / 2 mole KClO3,

31.998 g O2 / 1 mole O2.

Step-by-step explanation:

First, let's convert 10 g of KClO3 to moles using the molar mass of KClO3 which is 122.5 g/mol:

`10\text{ g KClO}_3\cdot\frac{1\text{ mol KClO}_3}{122.5\text{ g KClO}_3}=0.082\text{ moles KClO}_3.`

Now you can see in the chemical equation that 2 moles of KClO3 reacted produces 3 moles of O2, so we state a rule of three to find the number of moles of O2:

`\begin{gathered} 2\text{ mole KClO}_3\rightarrow3\text{ mole O}_2 \\ 0.082\text{ moles KClO}_3\rightarrow?\text{ mole O}_2 \end{gathered}`

The calculation of this will look like this:

`0.082\text{ mole KClO}_3\cdot\frac{3\text{ mole O}_2}{2\text{ mole KClO}_3}=0.12\text{3 moles O}_2.`

The final step to finding the mass of oxygen (O2) is using its molar mass which is 32 g/mol, like this:

`0.123\text{ mole O}_2\cdot\frac{32\text{ g O}_2}{1\text{ mol O}_2}=3.94\text{ g O}_2.`

As you can see from this process, the needed ratios are:

1 mole KClO3 / 122.55 g KClO3,

3 mole O2 / 2 mole KClO3,

31.998 g O2 / 1 mole O2. (in the explanation is approximated)