Gases, rates and equilibrium

Written by Dr. Ayesha Nadeem (Chemistry)

ECAT · Chemistry · 10 questions

Name: ____________________ Date: ____________

What volume does 1 mole of an ideal gas occupy at 273 K and 1 atm?
- A 11.2 L
- B 24 L
- C 22.4 L
- D 1 L
According to Boyle's law, if the pressure of a gas is doubled at constant temperature, its volume:
- A Doubles
- B Stays the same
- C Becomes four times
- D Halves
For a first order reaction, the half-life:
- A Is independent of the starting concentration
- B Depends on the starting concentration
- C Is zero
- D Doubles each half-life
Which is the expression for Kc of the reaction N2O4 <-> 2NO2?
- A [N2O4] / [NO2]^2
- B [NO2]^2 / [N2O4]
- C [NO2] / [N2O4]
- D [NO2]^2 x [N2O4]
In a buffer solution, pH = pKa when:
- A [A-] equals [HA]
- B [HA] is zero
- C [A-] is twice [HA]
- D The solution is neutral
Hess's law says that the enthalpy change of a reaction:
- A Is always negative
- B Depends on the path taken
- C Is the same whether it takes place in one step or several
- D Depends only on the catalyst
Which solution has the highest boiling point at the same molality?
- A Urea
- B Glucose
- C Sodium chloride
- D Calcium chloride
At constant temperature, if the pressure of a gas is doubled its volume becomes:
- A Double
- B One quarter
- C Unchanged
- D Half
The volume of 1 mole of an ideal gas at STP is:
- A 22.4 dm³
- B 24 dm³
- C 1 dm³
- D 11.2 dm³
The number of moles in 4 g of NaOH is: (Na = 23, O = 16, H = 1)
- A 1
- B 0.4
- C 4
- D 0.1

Answer key

1. C, 2. D, 3. A, 4. B, 5. A, 6. C, 7. D, 8. D, 9. A, 10. D

The molar volume of an ideal gas at 273 K and 1 atm is 22.4 litres.
At constant temperature, pressure times volume is constant, so doubling the pressure halves the volume.
The half-life of a first order reaction is 0.693 / k, which does not depend on concentration.
Kc is products over reactants, with each concentration raised to the power of its coefficient.
By the Henderson-Hasselbalch equation, pH = pKa + log([A-] / [HA]), and the log term is zero when the two are equal.
Enthalpy is a state function, so only the starting and final states matter.
Boiling point elevation depends on the number of particles. CaCl2 gives three ions, NaCl gives two, and glucose and urea do not ionise.
Boyle's law: pressure and volume are inversely proportional.
This is the molar volume at standard temperature and pressure.
Molar mass is 40 g/mol, so 4 ÷ 40 = 0.1 mol.