Answer:
739.8 mmHg
Explanation:
By Dalton's Law of Partial Pressures, the total pressure of a gas mixture is the sum of the partial pressure of its components. The partial pressure is the pressure that the substance would have if it was alone in the same conditions of the mixture (same temperature and volume). So:
[tex]P_{total} = P_{H_{2}O} + P_{H_{2}}[/tex]
757.3 = 17.5 + [tex]P_{H_{2}}[/tex]
[tex]P_{H_{2}}[/tex] = 757.3 - 17.5
[tex]P_{H_{2}}[/tex] = 739.8 mmHg