Question

How many grams of calcium chloride would you need to make 1 L of solution containing 5 ppm calcium (Ca)?

Answer 1

Explanation:

The given data is as follows.

           Volume = 1 L,    Concentration of Ca = 5 ppm or 5 mg/L

As 1 mg = 0.001 g so, 5 mg /L will be equal to 0.005 g/l. Molar mass of calcium is 40.078 g/mol.

Hence, calculate molarity of calcium as follows.

           Molarity of Ca = $\frac{\text{given concentration}}{\text{molar mass}}$

                                  = $\frac{0.005 g/l}{40.078 g/mol}$

         Molarity of Ca = $1.25 \times 10^{-4} M$

Hence, molarity of $CaCl_{2}$ is $1.25 \times 10^{-4} M$. Since, volume is same so, moles of calcium chloride will be $1.25 \times 10^{-4} mol$.

Thus, we can conclude that mass of $CaCl_{2}$ will be as follows.

             $1.25 \times 10^{-4} \times 110.984$       (molar mass of $CaCl_{2}$ = 110.984 g/mol)

               = 0.0138 g

Thus, we can conclude that mass of $CaCl_{2}$ is 0.0138 g.