Chapter 3, Problem 3.25QP

A friend asks if you would be willing to check several homework problems to see if she is on the right track. Following are the problems and her proposed solutions. When you identify the problem with her work, make the appropriate correction.

1. a Calculate the number of moles of calcium in 27.0 g of Ca.

$27.0\text{g}\text{Ca}\times \frac{1\text{mol}\text{Ca}}{6.022\times {10}^{23}\text{g}\text{Ca}}=?$

1. b Calculate the number of potassium ions in 2.5 mol of K₂SO₄.

$\begin{array}{l}\begin{array}{lll}2.5\text{mol}{\text{K}}_2{\text{SO}}_{\text{4}}\hfill & \times \hfill & \frac{1\text{mol}{\text{K}}^{+}\text{ions}}{1\text{mol}{\text{K}}_2{\text{SO}}_4}\hfill \\ \hfill & \times \hfill & \frac{6.022\times {10}^{23}{\text{K}}^{+}\text{ions}}{1\text{mol}{\text{K}}^{+}\text{ions}}=?\hfill \end{array}\\ \end{array}$

1. c Sodium reacts with water according to the following chemical equation.

$2\text{Na}+2{\text{H}}_2\text{O}\to {\text{H}}_2+2\text{NaOH}$

Assuming complete reaction, calculate the number of moles of water required to react with 0.50 mol of Na.

$0.50\text{mol}\text{Na}\times \frac{1\text{mol}{\text{H}}_2\text{O}}{2\text{mol}\text{Na}}=?$