Gas Laws Fact Sheet

[tex]
\[
\begin{array}{|c|c|}
\hline
\text{Ideal gas law} & P V = n R T \\
\hline
\multirow{3}{*}{\text{Ideal gas constant}} & \\
\hline
& \\
\hline
& R = 0.0821 \, \frac{\text{L atm}}{\text{mol K}} \\
\hline
\text{Standard atmospheric pressure} & 1 \, \text{atm} = 101.3 \, \text{kPa} \\
\hline
\text{Celsius to Kelvin conversion} & K = { }^{\circ} C + 273.15 \\
\hline
\end{array}
\]
[/tex]

Select the correct answer.

When a chemist collects hydrogen gas over water, she ends up with a mixture of hydrogen and water vapor in her collecting bottle. If the pressure in the collecting bottle is 97.1 kilopascals and the vapor pressure of the water is 3.2 kilopascals, what is the partial pressure of the hydrogen?

A. [tex]\( 93.9 \, \text{kPa} \)[/tex]

B. [tex]\( 98.1 \, \text{kPa} \)[/tex]

C. [tex]\( 100.3 \, \text{kPa} \)[/tex]

To find the partial pressure of hydrogen gas collected over water, we need to use the concept of partial pressures. The total pressure in the collecting bottle is made up of two parts: the pressure of the hydrogen gas and the vapor pressure of the water.

Here are the steps to solve the problem:

1. Understand the Total Pressure:
- The total pressure inside the collecting bottle is the combined pressure exerted by both the hydrogen gas and the water vapor. This total pressure is given as 97.1 kilopascals (kPa).

2. Identify the Vapor Pressure of Water:
- The vapor pressure of the water is given as 3.2 kilopascals (kPa).

3. Calculate the Partial Pressure of Hydrogen:
- To find the partial pressure of the hydrogen gas, subtract the vapor pressure of the water from the total pressure in the collecting bottle.

[tex]\[
\text{Partial Pressure of Hydrogen} = \text{Total Pressure} - \text{Vapor Pressure of Water}
\][/tex]

[tex]\[
\text{Partial Pressure of Hydrogen} = 97.1 \, \text{kPa} - 3.2 \, \text{kPa} = 93.9 \, \text{kPa}
\][/tex]

Therefore, the partial pressure of the hydrogen gas is 93.9 kilopascals (kPa). The correct answer is option A: 93.9 kPa.