Question

Determine the number of moles of a gas which occupies 39.0mL at 27°C if the pressure is 107 kPa.

Answer 1

We can use the ideal gas law equation to solve for the number of moles present 
PV = nRT
P - pressure - 107 kPa
V - 39.0 x 10⁻⁶ m³
n - number of moles 
R - 8.314 Jmol⁻¹K⁻¹
T - temperature in K - 27 °C + 273 = 300 K
Substituting these values into the equation
107 000 Pa x 39.0 x 10⁻⁶ m³ = n x 8.314 Jmol⁻¹K⁻¹ x 300 K
n = 1.67 x 10⁻³ mol