What is the partial pressure of H2 gas (atm), collected over water at an atmospheric pressure of 1.022 atm and a temperature of 21.0°C? The partial pressure of water vapor is 18.65 mm Hg at 21.0°C.
Ideal and Real Gases
Ideal gases obey conditions of the general gas laws under all states of pressure and temperature. Ideal gases are also named perfect gases. The attributes of ideal gases are as follows,
Gas Laws
Gas laws describe the ways in which volume, temperature, pressure, and other conditions correlate when matter is in a gaseous state. The very first observations about the physical properties of gases was made by Robert Boyle in 1662. Later discoveries were made by Charles, Gay-Lussac, Avogadro, and others. Eventually, these observations were combined to produce the ideal gas law.
Gaseous State
It is well known that matter exists in different forms in our surroundings. There are five known states of matter, such as solids, gases, liquids, plasma and Bose-Einstein condensate. The last two are known newly in the recent days. Thus, the detailed forms of matter studied are solids, gases and liquids. The best example of a substance that is present in different states is water. It is solid ice, gaseous vapor or steam and liquid water depending on the temperature and pressure conditions. This is due to the difference in the intermolecular forces and distances. The occurrence of three different phases is due to the difference in the two major forces, the force which tends to tightly hold molecules i.e., forces of attraction and the disruptive forces obtained from the thermal energy of molecules.
![### Determining the Partial Pressure of H₂ Gas
**Problem Statement:**
What is the partial pressure of H₂ gas (in atm), collected over water at an atmospheric pressure of 1.022 atm and a temperature of 21.0°C? The partial pressure of water vapor is 18.65 mm Hg at 21.0°C.
**Solution:**
To find the partial pressure of H₂ gas collected over water, we need to subtract the partial pressure of the water vapor from the total atmospheric pressure.
1. **Convert the partial pressure of water vapor to atm:**
\[
\text{Partial pressure of water vapor} = 18.65 \, \text{mm Hg}
\]
\[
1 \, \text{atm} = 760 \, \text{mm Hg}
\]
\[
\text{Partial pressure of water vapor in atm} = \frac{18.65 \, \text{mm Hg}}{760 \, \text{mm Hg/atm}} \approx 0.0245 \, \text{atm}
\]
2. **Subtract the partial pressure of water vapor from the total atmospheric pressure:**
\[
\text{Total atmospheric pressure} = 1.022 \, \text{atm}
\]
\[
\text{Partial pressure of H₂ gas} = \text{Total atmospheric pressure} - \text{Partial pressure of water vapor}
\]
\[
\text{Partial pressure of H₂ gas} = 1.022 \, \text{atm} - 0.0245 \, \text{atm} \approx 0.9975 \, \text{atm}
\]
**Result:**
The partial pressure of H₂ gas is approximately **0.9975 atm**.
**Explanation:**
In this problem, the total atmospheric pressure is given, and so is the partial pressure of water vapor at a given temperature. The key is to recognize that the total atmospheric pressure is the sum of the partial pressures of all gases present, including water vapor. By subtracting the water vapor's partial pressure from the total, we are left with the partial pressure of the hydrogen gas.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F19b0aed3-745e-4879-8577-ea35399669d0%2F28332ba9-b634-4ab3-a423-71598b097227%2F52bqm2_processed.png&w=3840&q=75)
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