Q. 7.31 - An Introduction to General, Organic, and Biological Chemistry

Question

a. The compound ${\mathrm{MgSO}}_4$, Epsom salts, is used to soothe sore feet and muscles. How many grams will you need to prepare a bath containing $5.00$ mole of Epsom salts?

b. Potassium iodide, $\mathrm{KI}$, is used as an expectorant. How many grams are in $0.450$ mole of potassium iodide?

Step-by-Step Solution

Answer

(a) The $602$ g is needed to prepare a bath containing $5.00$ mole of Epsom salts

(b) The $74.7$ g are in $0.450$ mole of potassium iodide

Part (a) Step 1: Given information

We need to find the amount needed to prepare a bath containing $5.00$ mole of Epsom salts

Part (a) Step 2: Simplify

We know that

A mole is equal to molar mass

And molar mass of Epsom salt is, $120.38 \mathrm{g}/\mathrm{mol}$

Therefore, the amount needed to prepare a bath containing $5.00$ mole of Epsom salts is, $120.38 \frac{\mathrm{g}}{\cancel{\mathrm{mol}}}\times 5 \cancel{\mathrm{mol}}=602 \mathrm{g}$

Part (b) Step 1: Given information

We need to find the mass in $0.450$ mole of potassium iodide

Part (b) Step 2: Simplify

We know that

A mole is equal to molar mass

And molar mass of potassium iodide is, $166$ g

Therefore, the mass in $0.450$ mole of potassium iodide is, $166 \frac{\mathrm{g}}{\cancel{\mathrm{mol}}}\times 0.45 \cancel{\mathrm{mol}}=74.7 \mathrm{g}$