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A 642 mL sample of oxygen gas at 23.5°C and 795 mm Hg, is heated to 31.7°C and the volume of the gas expands to 957 mL. What is the new pressure in atm?

A) 0.723 atm

B) 0.932 atm

C) 3.05 atm

D) 5.19 atm

We can use combined gas law,

PV/T = k (constant)

Where, P is the pressure of the gas, V is volume of the gas and T is the temperature of the gas in Kelvin.

For two situations, we can use that as,

P₁V₁/T₁ = P₂V₂/T₂

P₁ = 795 mm Hg

V₁ = 642 mL

T₁ = (273 + 23.5) K = 296.5 K

P₂ = ?

V₂ = 957 mL

T₂ = (273 + 31.7) K = 304.7 K

From substitution,

795 mm Hg x 642 mL / 296.5 K = P₂ x 957 mL / 304.7 K

P₂ = 548.072 mm Hg

760 mmHg = 1 atm

548.072 mm Hg = 1 atm x (548.072 mmHg / 760 mmHg)

= 0.721 atm

Pressure of Oxygen gas is 0.721 atm.

Answer is "A"

Here, we made an assumption that oxygen gas has an ideal gas behavior.