Question

Assuming the air behaves like an ideal gas having an average molar mass of 29g per mole, calculate the mass of air in a flask of volume 267ml at a laboratory pressure of 715torr and a temperature of 21°C

Answer 1

Answer: To calculate the mass of air in the flask, we can use the ideal gas law:

PV = nRT

where:

P = pressure (in atm)

V = volume (in liters)

n = number of moles of air

R = ideal gas constant (0.0821 L atm/mol K)

T = temperature (in Kelvin)

Step 1: Convert the given pressure, volume, and temperature to the appropriate units.

Given pressure = 715 torr

Given volume = 267 ml

Given temperature = 21°C

Convert pressure to atm:

Pressure = 715 torr / 760 torr/atm ≈ 0.9408 atm

Convert volume to liters:

Volume = 267 ml / 1000 ml/L = 0.267 L

Convert temperature to Kelvin:

Temperature in Kelvin = 21°C + 273.15 ≈ 294.15 K

Step 2: Calculate the number of moles of air (n) using the ideal gas law:

PV = nRT

n = (PV) / RT

n = (0.9408 atm * 0.267 L) / (0.0821 L atm/mol K * 294.15 K)

n ≈ 0.0119 moles

Step 3: Calculate the mass of air using the given average molar mass of air (29 g/mol):

Mass of air = number of moles * molar mass

Mass of air ≈ 0.0119 moles * 29 g/mol ≈ 0.3451 g

So, the mass of air in the flask is approximately 0.3451 grams.