Mastering the Ideal Gas Equation: Overcoming Unit Conversion Challenges

Ideal Gas Equation

Ideal Gas Equation Calculations

PV = n R T

A common obstacle for students regarding the ideal gas equation is the conversion of units.

P = Pressure (Pa)

V = Volume (m³)

n = Number of moles of gas

R = Gas Constant = 8.31 Jmol⁻¹K⁻¹

Unit Conversion

Pressure (Pascals - Pa)

Kilopascals (KPa) to Pascals (Pa)

The prefix 'Kilo' denotes a factor of 1000 or 10³

Therefore, 1 KPa = 1000 Pa

Convert KPa to Pa by multiplying by 1000

Megapascals to Pascals

The prefix 'Mega' denotes a factor of 10⁶ or 1,000,000

Therefore, 1 MPa = 10⁶ Pa

Convert MPa to Pa by multiplying by 1,000,000

Volume (m³)

dm³ to cm³

1 dm = 10 cm (×10)

Thus, 1 dm³ = 1000 cm³ (×10³)

Convert dm³ to cm³ by multiplying by 1000

m³ to cm³

1 m = 100 cm (×100)

Thus, 1 m³ = 1,000,000 cm³ (×100³)

Convert m³ to cm³ by multiplying by 1,000,000

Temperature (K)

25°C = 298 K

Convert °C to K by adding 273

Example

Calculate the volume of 64g of Oxygen gas in cm³ at a temperature of 30°C and pressure of 500 KPa. R = 8.31 Jmol⁻¹K⁻¹

1. Determine moles of Oxygen

Moles = Mass ÷ Molar mass (Mr)

Moles = 64 ÷ 32 = 2

2. Convert T and P to appropriate units

30°C = 303 K

500 KPa = 500,000 Pa

3. Apply the Ideal Gas Equation

PV = nRT

V = nRT ÷ P

V = 2×8.31×298 ÷ 500,000

V = 0.00991 m³

4. Convert m³ to cm³

V = 0.00991 m³ = 0.00991 × 1,000,000

V = 9910 cm³