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AS & A Level · AS/A Level

Chemistry

Quantitative and physical chemistry

Name: ____________________Date: October 10, 2026
  1. 1.

    25.0 cm^3 of NaOH is neutralised by 20.0 cm^3 of 0.100 mol dm^-3 HCl. The reaction is 1:1. Calculate the NaOH concentration.

    [3 marks]
  2. 2.

    For H2(g) + I2(g) <=> 2HI(g), equilibrium concentrations are [H2] = 0.20, [I2] = 0.10 and [HI] = 0.60 mol dm^-3. Write Kc, calculate its value and determine its units.

    [4 marks]
  3. 3.

    A buffer contains 0.100 mol HA and 0.150 mol A^- with pKa = 4.76. Add 0.0100 mol HCl without changing volume significantly. Assuming complete reaction with A^-, calculate the new pH using pH = pKa + log10([A^-]/[HA]) and explain how buffering occurs.

    [5 marks]

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