Question

grams of potassium hydroxide are expected to be produced if 3.1 g of potassium oxide has reacted completely.

Explanation:

Step1: Write the balanced chemical equation

$K_2O + H_2O=2KOH$

Step2: Calculate molar masses

Molar mass of $K_2O$: $2\times39.1 + 16=94.2\ g/mol$. Molar mass of $KOH$: $39.1+16 + 1=56.1\ g/mol$

Step3: Calculate moles of $K_2O$

$n_{K_2O}=\frac{m_{K_2O}}{M_{K_2O}}=\frac{3.1\ g}{94.2\ g/mol}\approx0.033\ mol$

Step4: Determine moles of $KOH$ based on mole - ratio

From the balanced equation, mole - ratio of $K_2O$ to $KOH$ is $1:2$. So $n_{KOH}=2\times n_{K_2O}=2\times0.033\ mol = 0.066\ mol$

Step5: Calculate mass of $KOH$

$m_{KOH}=n_{KOH}\times M_{KOH}=0.066\ mol\times56.1\ g/mol\approx3.7\ g$

Answer:

$3.7\ g$