When applying the combined gas law, which variable is assumed to remain constant?

• A. The pressure
• B. The volume
• C. The amount of gas (number of moles)
• D. The temperature

Answer: (C)

Verified step by step guidance

1. Recall that the combined gas law relates pressure (P), volume (V), and temperature (T) of a gas sample, combining Boyle's, Charles's, and Gay-Lussac's laws into one equation.
2. The combined gas law is expressed as \(\frac{P_1 \times V_1}{T_1} = \frac{P_2 \times V_2}{T_2}\), where subscripts 1 and 2 refer to initial and final states.
3. Notice that the combined gas law does not include the amount of gas (number of moles, n) explicitly in the equation.
4. This means that when using the combined gas law, the amount of gas (n) is assumed to remain constant throughout the process.
5. Therefore, the variable assumed constant in the combined gas law is the number of moles of gas.