1. Determine the molar ratio of hydrogen to (NH4)2CO3. From the chemical formula (NH4)2CO3, we see that there are 2 moles of NH4+ ions and 1 mole of CO3^2- ions per mole of (NH4)2CO3. Each NH4+ ion contains 4 moles of hydrogen atoms.
2. Calculate the total number of moles of hydrogen in 3.5 moles of (NH4)2CO3. Multiply the number of moles of (NH4)2CO3 by the molar ratio of hydrogen to (NH4)2CO3.
$$ \text{Moles of H} = 3.5 \text{ mol (NH}_4)_2\text{CO}_3 \times \frac{8 \text{ mol H}}{1 \text{ mol (NH}_4)_2\text{CO}_3 }$$ $$ \text{Moles of H} = 28 \text{ mol H}$$
Therefore, there are 28 moles of hydrogen in 3.5 moles of (NH4)2CO3.
