Mole Fraction, Pressure & Temperature, and STP ✏ Chemistry In a Nutshell

Rucete ✏ Chemistry In a Nutshell

1. Mole Fraction (χA)

• Definition: Ratio of the moles of one gas to the total moles of gases in a mixture.

• Formula:

  $$χ_A = \frac{n_A}{n_{\text{total}}}$$
  • $χ_A$ = Mole fraction of gas A
  • $n_A$ = Moles of gas A
  • $n_{\text{total}}$ = Total moles of all gases

• Relationship with Partial Pressure:

  $$P_A = χ_A \cdot P_{\text{total}}$$
  • $P_A$ = Partial pressure of gas A
  • $P_{\text{total}}$ = Total pressure of gas mixture

2. Pressure and Temperature

• Standard Atmospheric Conditions (Normal conditions):

  • Temperature: 25°C (298 K)
  • Pressure: 1 atm

• Pressure Unit Conversions:

  • 1 atm = 760 mmHg = 101.325 kPa
  • 1 torr = 1 mmHg

• Temperature Conversion Formula:

  $$T(K) = T(°C) + 273$$
  • Example: 0°C = 273 K

3. Standard Temperature and Pressure (STP)

• STP Conditions:
  • Temperature: 0°C (273 K)
  • Pressure: 1 atm
• At STP, 1 mole of gas occupies 22.41 L.
• Avogadro's Number: $6.02 \times 10^{23}$ gas molecules per mole.

In a Nutshell

• Mole fraction = Part/Total
• STP = 0°C, 1 atm
• 1 mole of gas = 22.41 L at STP