Chapter EH, Problem 19R

Solution

Interpretation: The amount of calcium present in a person with a total mass of 68 kg needs to be determined.

Concept Introduction:

The mass percentage of any substance can be estimated as follows:

  $\%m_{\text{A}}=\frac{m_{\text{A}}}{\text{total mass}}\times 100\%$

Here, $m_{\text{A}}$ is the mass of that substance.

1.02 kg.

The mass percent of Ca in a human’s body mass is 1.5%. The total mass or body mass of a person is given 68 kg thus, the mass percent of Ca in the body can be calculated as follows:

  $\%m_{\text{Ca}}=\frac{m_{\text{Ca}}}{m_{\text{body}}}\times 100\%$

Rearrange the above equation.

  $m_{\text{Ca}}=\frac{\%m_{\text{Ca}}\times m_{\text{body}}}{100\%}$

Substitute the values,

  $\begin{array}{c}{m}_{\text{Ca}}=\frac{1.5\%\times 68\text{ kg}}{100\%}\\ =1.02\text{ kg}\end{array}$

Therefore, the mass of calcium in the human body is 1.02 kg.