4. What is the percent composition by mass of hydrogen in NH_(4)HCO_(3)(molar mass=79 g/mol) ? 5.1% 50% 6.3% 10%

To find the percent composition by mass of hydrogen in \( \mathrm{NH}_{4} \mathrm{HCO}_{3} \), we need to determine the total mass of hydrogen in one mole of the compound and then divide it by the molar mass of the compound.<br /><br />1. **Calculate the molar mass of hydrogen in \( \mathrm{NH}_{4} \mathrm{HCO}_{3} \):**<br /><br /> - The formula \( \mathrm{NH}_{4} \mathrm{HCO}_{3} \) contains 5 hydrogen atoms (4 from \( \mathrm{NH}_{4}^+ \) and 1 from \( \mathrm{HCO}_{3}^- \)).<br /> - The atomic mass of hydrogen is approximately \( 1 \, \mathrm{g/mol} \).<br /><br /> Therefore, the total mass of hydrogen in one mole of \( \mathrm{NH}_{4} \mathrm{HCO}_{3} \) is:<br /> \[<br /> 5 \times 1 = 5 \, \mathrm{g/mol}<br /> \]<br /><br />2. **Calculate the percent composition by mass of hydrogen:**<br /><br /> \[<br /> \text{Percent composition of hydrogen} = \left( \frac{\text{Mass of hydrogen}}{\text{Molar mass of } \mathrm{NH}_{4} \mathrm{HCO}_{3}} \right) \times 100\%<br /> \]<br /><br /> \[<br /> = \left( \frac{5}{79} \right) \times 100\% \approx 6.33\%<br /> \]<br /><br />Therefore, the percent composition by mass of hydrogen in \( \mathrm{NH}_{4} \mathrm{HCO}_{3} \) is approximately \( 6.3\% \).