Final answer:
In three formula units of ammonium benzoate, there are a total of 27 hydrogen atoms.
Step-by-step explanation:
The question asks how many hydrogen atoms are in three formula units of ammonium benzoate, which has the formula C₆H₅COONH₄. To find the total number of hydrogen atoms, we need to count the hydrogen atoms in both the benzoate ion (C₆H₅COO-) and the ammonium ion (NH₄+). There are 5 hydrogens in the benzene ring (C₆H₅), another one in the carboxyl group (-COOH), making it 6 hydrogens for the benzoate ion. However, since the carboxyl group loses a hydrogen to become a carboxylate anion (-COO-), we only count 5 hydrogens for the benzoate ion. For the ammonium ion (NH₄+), as per the subscript, there are 4 hydrogen atoms. Therefore, for one formula unit, the total hydrogen count is 5 (from benzoate) + 4 (from ammonium), which equals 9. For three formula units, we multiply this by 3, yielding 27 hydrogen atoms.