Question

name: ____________ date: 2/9/26 per: 5
stoichiometry practice 2 - mass to mass calculations
directions: for each of the following problems, use the balanced chemical equation to answer the questions.

1. how many grams of potassium oxide ($k_2o$) will be formed from 34.3 grams of potassium, according to the following reaction:

$4k + o_2 \
ightarrow 2k_2o$
$\frac{34.3g\\ k}{1} \times \frac{1mol\\ k}{39.098} \times \frac{mol\\ o_2}{mol\\ k} \times \frac{go_2}{1mol\\ o_2} =$

Explanation:

Step1: Convert mass K to moles

Molar mass of K is $39.098\ \text{g/mol}$.
$\text{Moles of K} = \frac{34.3\ \text{g}}{39.098\ \text{g/mol}} \approx 0.877\ \text{mol}$

Step2: Mole ratio of K to K₂O

From $4\text{K} + \text{O}_2
ightarrow 2\text{K}_2\text{O}$, ratio is $\frac{2\ \text{mol K}_2\text{O}}{4\ \text{mol K}} = \frac{1\ \text{mol K}_2\text{O}}{2\ \text{mol K}}$.
$\text{Moles of K}_2\text{O} = 0.877\ \text{mol K} \times \frac{1\ \text{mol K}_2\text{O}}{2\ \text{mol K}} \approx 0.4385\ \text{mol}$

Step3: Calculate molar mass of K₂O

Molar mass = $2\times39.098 + 16.00 = 94.196\ \text{g/mol}$

Step4: Convert moles K₂O to mass

$\text{Mass of K}_2\text{O} = 0.4385\ \text{mol} \times 94.196\ \text{g/mol}$
$\text{Mass of K}_2\text{O} \approx 41.3\ \text{g}$

Answer:

Approximately 41.3 grams of potassium oxide will be formed.