Question

A reaction of 0.028 g of magnesium with excess hydrochloric acid generated 31.0 mL of hydrogen gas. The gas was collected by water displacement in a 22 °C water bath. The barometric pressure in the lab that day was 746 mm Hg.Use Dalton's law to calculate the partial pressure of hydrogen gas in the gas-collecting tube.

Answer 1

Answer : The partial pressure of
`H_2` is, 726.2 mmHg

Solution :

According to the Dalton's law, the total pressure of the gas is equal to the sum of the partial pressure of the mixture of gasses.

`P_T=p_(H_2)+p_(H_2O)`

where,

`P_T` = total partial pressure = barometric pressure = 746 mmHg

`P_(H_2)` = partial pressure of hydrogen gas = ?

`P_(H_2O)` = partial pressure of water vapor = 19.8 mmHg (assume)

Now put all the given values is expression, we get the partial pressure of the hydrogen gas.

`746mmHg=p_(H_2)+19.8mmHg`

`p_(H_2)=726.2mmHg`

Therefore, the partial pressure of
`H_2` is, 726.2 mmHg