Answer : The partial pressure of the hydrogen is, 705.9 mmHg
Explanation :
According to the Dalton's law of partial pressure,

where,
= total pressure of the gas = 729.7 mmHg
= partial pressure of the hydrogen gas = ?
= partial pressure of the water = 23.8 mmHg (standard value)
Now put all the given values in the above expression, we get:


Therefore, the partial pressure of the hydrogen is, 705.9 mmHg