Calculating New Volume Using the Combined Gas Law

PhysicsCombined Gas LawMediumSTEM

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Imagine a gas sees an increase of temperature from $20^\circ C$ to $50^\circ C$. This causes the pressure to increase from $120$ torr to $670$ torr. If the volume was $3.8$ liters, what will be the new volume?

A) $9.5$ liters

B) $1.5$ liters

C) $30$ liters

D) $3.6$ liters

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Step by Step Written Solution

1
Step 1

In this problem, we're looking at a gas undergoing changes in pressure, volume, and temperature. We need to find the final volume given the initial and final states.

Gas Laws Calculation

2
Step 2

To solve this, we use the Combined Gas Law, which relates the initial and final pressure, volume, and temperature of a fixed amount of gas.

$$ \frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2}$$
3
Step 3

Let's list our known values from the problem. The initial pressure is one hundred twenty torr, and the initial volume is three point eight liters.

Known Values

$$P_1 = 120 \; \text{torr}$$
$$V_1 = 3.8 \; \text{L}$$
4
Step 4

The final pressure increases to six hundred seventy torr.

$$P_2 = 670 \; \text{torr}$$
5
Step 5

Important note: when working with gas laws, temperature must always be in Kelvin. To convert from Celsius to Kelvin, we add two hundred seventy-three point fifteen.

$$T(K) = T(^ \circ C) + 273.15$$
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Step 6

So, our initial temperature of twenty degrees Celsius becomes two hundred ninety-three point fifteen Kelvin.

$$T_1 = 20 + 273.15 = 293.15 \; \text{K}$$
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Step 7

And the final temperature of fifty degrees Celsius becomes three hundred twenty-three point fifteen Kelvin.

$$T_2 = 50 + 273.15 = 323.15 \; \text{K}$$
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Step 8

Now, we rearrange the Combined Gas Law formula to isolate the final volume, V sub two.

$$ \frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2}$$
$$ V_2 = \frac{P_1 V_1 T_2}{T_1 P_2}$$

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About This Question

Subject
Physics
Topic
Combined Gas Law
Difficulty
Medium
Exam
STEM
Question Type
Multiple Choice

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