Question

Use Dalton’s law and the vapor pressure of water at 22 °C (Table 1) to calculate the partial pressure of hydrogen gas in the gas collecting tube.

Answer 1

The partial pressure of hydrogen gas in the gas collecting tube can be calculated using Dalton's law and the vapor pressure of water at 22°C.

Step-by-step explanation:

Solution

We need to take into account that the total pressure includes the vapor pressure of water. According to Table 6.7.1, the vapor pressure of water at 22°C is 19.84 torr. According to Dalton's law of partial pressures (Equation 6.7.1), the total pressure equals the sum of the pressures of the individual gases, so

Pg=PTotal-PH₂0

In order to solve a problem, it is necessary to know the vapor pressure of water at the temperature of the reaction (see table below). The sample problem illustrates the use of Dalton's Law when a gas is collected over water.