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------------------------------------------------ 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]98.2 \text{ kPa}[/tex]
C. [tex]100.3 \text{ kPa}[/tex]
D. [tex]104.5 \text{ kPa}[/tex]

To find the partial pressure of hydrogen gas when collecting it over water, we use the principle that the total pressure in a container is the sum of the partial pressures of all the gases present. In this case, the total pressure is the sum of the partial pressure of hydrogen and the vapor pressure of water.

Here's how you can calculate the partial pressure of hydrogen:

1. Identify the total pressure in the collecting bottle:
The total pressure given in this scenario is 97.1 kilopascals (kPa).

2. Identify the vapor pressure of water:
The vapor pressure of water is provided as 3.2 kilopascals (kPa).

3. Apply Dalton's Law of Partial Pressures:
According to Dalton's law, the partial pressure of hydrogen is equal to the total pressure minus the vapor pressure of the water:
[tex]\[
\text{Partial pressure of hydrogen} = \text{Total pressure} - \text{Vapor pressure of water}
\][/tex]

4. Calculate the partial pressure of hydrogen:
[tex]\[
\text{Partial pressure of hydrogen} = 97.1 \, \text{kPa} - 3.2 \, \text{kPa} = 93.9 \, \text{kPa}
\][/tex]

Thus, the partial pressure of the hydrogen gas is [tex]$93.9 \, \text{kPa}$[/tex].

The correct answer is:
A. [tex]$93.9 \, \text{kPa}$[/tex]