Answer to Question #318533 in General Chemistry for zzz

Question

How many moles of helium would give a pressure of 900 mm Hg in 25.0 L vessel at

500C?

Answer 1

P(He) = 900 mm Hg = 119990 Pa = 119.99 kPa;

V(He) = 25.0 L;

T(He) = 500 C = 773 K;

R(gas constant) = 8.314 (kPa * L/(mol * K));

The ideal gas law is written in an empirical form:

P * V = n * R *T;

Therefore:

n(He) = P(He) * V(He)/(R * T(He)) = 119.99 * 25.0/(8.314 * 773) = 2999.75/6426.72 = 0.47 mol.

Answer: 0.47 mol.