400.0 mL of a gas is collected at 745.0 mm Hg. What will the volume be at standard pressure

(Std pressure = 760.0 mm Hg) ?

392.1 mL

Explanation:

Ideal gas law says:

PV = nRT

where P is absolute pressure, V is volume, n is amount of gas in moles, R is the universal gas constant, and T is absolute temperature.

If n, R, and T are held constant:

P₁ V₁ = P₂ V₂

Plugging in values:

(745.0 mmHg) (400.0 mL) = (760.0 mmHg) V

V = 392.1 mL