# What mass of "potassium chlorate" is necessary to generate a 5.5*g mass of oxygen gas?

Dec 21, 2017

Look at the stoichiometric equation....

#### Explanation:

$K C l {O}_{3} \left(s\right) + \Delta \stackrel{M n {O}_{2}}{\rightarrow} K C l \left(s\right) + \frac{3}{2} {O}_{2} \left(g\right)$

A little $M n \left(+ I V\right)$ salt is usually added to catalyze the reaction....

We require $5.5 \cdot g$ dioxygen gas....a molar quantity of $\frac{5.5 \cdot g}{32.0 \cdot g \cdot m o {l}^{-} 1} = 0.0172 \cdot m o l$, and note that this is in respect to dioxygen gas....

And so we need $\frac{2}{3} \cdot \text{equiv}$ with respect to the chlorate....i.e. $\frac{2}{3} \times 0.0172 \cdot m o l \times 122.55 \cdot g \cdot m o {l}^{-} 1 = 14.0 \cdot g$

Dec 21, 2017

$= 14.04 g K C l {O}_{3}$

#### Explanation:

1. Write and balance the equation
$2 K C l {O}_{3} \to 2 K C l + 3 {O}_{2}$
2. First thing to do is to find the molar masses of the involved compounds. In this case, ${O}_{2}$ and $K C l {O}_{3}$. Refer to the periodic table for the elements' atomic masses.
${O}_{2} = \frac{32 g}{m o l}$
$K C l {O}_{3} = \frac{122.5 g}{m o l}$
3. Given the mass of ${O}_{2}$, as convention, convert $\text{mass} \left(m\right)$ to $\text{moles} \left(\eta\right)$ as basis for the usual series of conversions.
$= 5.5 \cancel{g {O}_{2}} \times \frac{1 m o l {O}_{2}}{32 \cancel{g {O}_{2}}}$
$= 0.1719 m o l {O}_{2}$
4. Now, since the target is the mKCl)_3, use $\eta {O}_{2}$ as basis with reference to the balanced equation for the mole ratio to find the $\eta K C l {O}_{3}$;i.e.,
$= 0.1719 \cancel{m o l {O}_{2}} \times \frac{2 m o l K C l {O}_{3}}{3 \cancel{m o l {O}_{2}}}$
$= 0.1146 m o l K C l {O}_{3}$
5. Finally, find $m K C l {O}_{3}$ through the relationship obtainable from the molar mass of $K C l {O}_{3}$; that is, $1 m o l K C l {O}_{3} \equiv 122.5 g K C l {O}_{3}$. Hence,
$= 0.1146 \cancel{m o l K C l {O}_{3}} \times \frac{122.5 g K C l {O}_{3}}{1 \cancel{m o l K C l {O}_{3}}}$
$= 14.04 g K C l {O}_{3}$
6. Therefore, $5.5 g {O}_{2}$ is produced in the decomposition of $14.04 g K C l {O}_{3}$.