Final answer:
One mole of (NH4)2HPO4 contains 5.42 x 10^24 atoms of hydrogen because each molecule of the compound has 9 hydrogen atoms and one mole of any substance contains Avogadro's number of entities.
Step-by-step explanation:
The formula (NH4)2HPO4 represents the compound diammonium hydrogen phosphate. To determine the number of hydrogen atoms in one mole of this compound, we can analyze its molecular formula. Each NH4 group contains 4 hydrogen atoms, and there are two such groups in the formula. Additionally, there is one extra hydrogen atom in the HPO4 part. Therefore, we have a total of 2 x 4 hydrogen atoms from the NH4 groups plus 1 hydrogen atom from HPO4, adding up to 9 hydrogen atoms per molecule.
Since one mole of any substance contains Avogadro's number of entities, which is approximately 6.02 x 1023, one mole of (NH4)2HPO4 contains 9 moles of hydrogen atoms. To calculate the total number of hydrogen atoms in one mole of (NH4)2HPO4, we multiply 9 by Avogadro's number:
9 moles of H atoms x 6.02 x 1023 atoms/mole = 5.42 x 1024 atoms of hydrogen.
Therefore, the correct answer is D. 5.42 x 1024 atoms of hydrogen.