Question

At 4.5 L sample of gas is at a temperature of 34 Celsius and a pressure of 840 mmHg. What is the new volume of the gas at STP?

Answer 1

Step 1

When all conditions of gas vary, it is used the general gas law. Mathematically:

P1 x V1/T1 = P2 x V2/T2 (1)

P = pressure

T = absolute temperature

V = volume

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Step 2

Data provided:

Conditions 1:

P1 = 840 mmHg

T1 = 34°C + 273 = 307 K

V1 = 4.5 L

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Conditions 2: STP conditions, therefore:

T2 = 0 °C + 273 = 273 K

P2 = 1 atm x (760 mmHg/1 atm) = 760 mmHg

(1 atm = 760 mmHg)

V2 = unknown

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Step 3

Procedure

From (1) V2 is cleared:

P1 x V1/T1 = P2 x V2/T2

(P1 x V1/T1)x T2/P2 = V2

(840 mmHg x 4.5 L/307 K) x (273 K/760 mmHg) = 4.42 L

Answer: V2 = 4.42 L