A sample of hydrogen gas in a flask of volume 25.0 mL has a pressure of 487.3 mm Hg at 20.5 o C. This sample is transferred into a flask of unknown volume. The pressure is measured to be 99.7 mm Hg and the temperature is raised to 24.5 o C in the new flask. What is the volume of the new flask

124 mL is the volume for the new flask

Explanation:

We can apply the Ideal Gases law for both situations where the volume of Hydrogen remains constant.

The formula is P . V = n . R . T

We despise n because, as we said the moles remain constant and R, because it is a value that never changes.

(P₁ . V₁) / T₁ = (P₂ . V₂) / T₂

Let's do unit's conversion:

20°C + 273 = 293K         487.3 mmHg . 1 atm / 760mmHg = 0.641 atm

24.5°C + 273 = 297.5K    99.7 mmHg. 1 atm / 760mmHg = 0.131 atm

25mL . 1L / 1000mL = 0.025L

We replace data:

(0.641 atm .  0.025L) / 293K = (0.131 atm . V₂) / 297.5K

[(0.641 atm .  0.025L) / 293K]  . 297.5K = 0.131 atm . V₂

0.0163 atm.L = 0.131 atm . V₂

V₂ = 0.0163 atm.L / 0.131 atm → 0.124L

We convert volume to mL → 0.124 L . 1000mL / 1L  = 124 mL

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