Question

A solution of ammonia and water contains 1.60×1025 water molecules and 6.80×1024 ammonia molecules. How many total hydrogen atoms are in this solution?

Answer 1

Water is \(H_2O\)
Ammonia is \(NH_3\)
As you can see from the molecular formulas, one molecule of ammonia contains 3 hydrogens and one molecule of water has 2hydrogens.
Just multiply those by your given number of their molecules to get total H atoms