Final answer:
To find the original pressure of helium gas, apply Gay-Lussac's law using the formula P1/T1 = P2/T2. Given the values, solve for P1 to determine the original pressure before the gas was cooled.
Step-by-step explanation:
The student's question is about using the gas laws to determine the original pressure of a helium gas sample when given the final pressure after a temperature change. To solve this, we apply Gay-Lussac's law, which states that the pressure of a gas is directly proportional to its temperature in kelvins (K), assuming volume and number of moles remain constant. Thus, the formula we will use is P1/T1 = P2/T2, where P1 and P2 represent the initial and final pressures, and T1 and T2 represent the initial and final temperatures, respectively.
Given that T1 = 237 K, T2 = 253 K, and P2 = 380 torr, we can rearrange the formula to solve for the initial pressure P1, yielding P1 = (P2 * T1) / T2. Substituting the given values and calculating gives us the original pressure of the gas.