How many hydrogen atoms are in each of the following: (a) \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH},(\mathbf{b}) \mathrm{Ca}\left(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{COO}\right)_{2},(\mathbf{c})\left(\mathrm{NH}_{4}\right)_{3} \mathrm{PO}_{4} ?\)

For each compound, we need to find the subscript that indicates the number of hydrogen atoms: (a) \(\mathrm{C}_2\mathrm{H}_5\mathrm{OH}\): We have two parts with hydrogen atoms: \(\mathrm{H}_5\) and \(\mathrm{OH}\). (b) \(\mathrm{Ca}\left(\mathrm{C}_2\mathrm{H}_5\mathrm{COO}\right)_2\): We have hydrogen atoms in \(\mathrm{C}_2\mathrm{H}_5\) and \(\mathrm{COO}\). (c) \(\left(\mathrm{NH}_4\right)_3\mathrm{PO}_4\): We have hydrogen atoms in \(\mathrm{NH}_4\).

Now, we will find the number of hydrogen atoms in each compound by multiplying the subscripts by any coefficients within the compound: (a) \(\mathrm{C}_2\mathrm{H}_5\mathrm{OH}\): Using both parts with hydrogen atoms, we have \(5 + 1\) hydrogen atoms. Therefore, there are 6 hydrogen atoms in this compound. (b) \(\mathrm{Ca}\left(\mathrm{C}_2\mathrm{H}_5\mathrm{COO}\right)_2\): Here, we need to consider the coefficients: For \(\mathrm{C}_2\mathrm{H}_5\), we have \(5\) hydrogen atoms, and for \(\mathrm{COO}\), we have \(1\) hydrogen atom (from the \(\mathrm{OH}\) part). Since there is a subscript \(2\) after the bracket, we will need to multiply the total number of hydrogen atoms by this coefficient: \((5 + 1) \cdot 2 = 12\). Therefore, there are 12 hydrogen atoms in this compound. (c) \(\left(\mathrm{NH}_4\right)_3\mathrm{PO}_4\): In this compound, we have \(4\) hydrogen atoms in \(\mathrm{NH}_4\). Since there is a subscript \(3\) after the bracket, we will need to multiply the total number of hydrogen atoms by this coefficient: \(4 \cdot 3 = 12\). Therefore, there are 12 hydrogen atoms in this compound. In conclusion, there are: (a) 6 hydrogen atoms in \(\mathrm{C}_2\mathrm{H}_5\mathrm{OH}\) (b) 12 hydrogen atoms in \(\mathrm{Ca}\left(\mathrm{C}_2\mathrm{H}_5\mathrm{COO}\right)_2\) (c) 12 hydrogen atoms in \(\left(\mathrm{NH}_4\right)_3\mathrm{PO}_4\)