Ammonia gas occupies a volume of 450 mL at a pressure of 90 kPa. What volume will it occupy at standard pressure?

Let's assume that the gas has an ideal gas behavior and the temperature of the gas remains constant.

We can use Boyle's law to solve this problem.

Boyle's law says "the pressure of a fixed amount of an ideal gas is inversely proportional to its volume when the temperature is constant".

P α 1/V

Where P is pressure of the gas and V is the volume of the gas.

Hence, we can use Boyle's law for two different situations as,

P₁V₁ = P₂V₂

P₁ = 90 kPa = 90 x 10³ Pa

V₁ = 450 mL

P₂ = Standard pressure = 1 atm = 101325 Pa

V₂ = ?

By applying the formula,

90 x 10³ Pa x 450 mL = 101325 Pa x V₂

V₂ = (90 x 10³ Pa x 450 mL) / 101325 Pa

V₂ = 399.7 mL

Hence, the volume of the ammonia gas at standard pressure is 399.7 mL.