Multiple Choice
If the pressure and the temperature of a gas are both decreased by 50%, what will happen to the volume of the gas according to the combined gas law (assuming the amount of gas remains constant)?
7. Gases
Chemistry Gas Laws: Combined Gas Law
Multiple Choice
In the combined gas law, which variable is assumed to remain constant?
A
The temperature (T)
B
The pressure (P)
C
The amount of gas (n)
D
The volume (V)
Verified step by step guidance1
Recall that the combined gas law relates pressure (P), volume (V), and temperature (T) of a gas sample, and is expressed as \(\frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2}\).
Notice that the combined gas law does not include the amount of gas (n) explicitly, which means it assumes the amount of gas remains constant during the process.
Understand that the combined gas law is derived from combining Boyle's law, Charles's law, and Gay-Lussac's law, all of which consider a fixed amount of gas.
Therefore, when using the combined gas law, the variable that is held constant is the amount of gas (n), while pressure, volume, and temperature can change.
Summarize that the combined gas law is useful for problems where the quantity of gas does not change, but pressure, volume, and temperature vary.
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