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
Mass of salt is equal to 218.8125 grams.
1mol=6.022x10^23 atoms
3.75mol= 6.022x3.75x10^23 atoms
=2.2583x10^24 atoms
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Number of Atoms in Gold for given mass can be calculated using following formula,
# of Moles = Number of Atoms / 6.022 × 10²³
Or,
Number of Atoms = Moles × 6.022 × 10²³ ------- (1)
Calculating Moles,
As,
Moles = Mass / M.mass
So,
Moles = 4.25 g / 196.96 g/mol
Moles = 0.0215
Putting value of mole in eq.1,
Number of Atoms = 0.0215 × 6.022 × 10²³
Number of Atoms = 1.299 × 10²²
Result:
4.25 g of Gold Nugget contains 1.299 × 10²² Atoms.