Reversing the calculations

3 marks · Easy

Potassium hydroxide reacts with nitric acid according to the equation:

25.0 cm³ of 0.200 mol/dm³ potassium hydroxide solution is mixed with 25.0 cm³ of 0.200 mol/dm³ nitric acid.

(a)

Calculate the number of moles of potassium hydroxide in the mixture.

[1 mark]

(b)

Calculate the number of moles of nitric acid in the mixture.

[1 mark]

(c)

State the simplest whole-number ratio of reactant volumes needed for complete neutralisation according to the equation.

[1 mark]

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

Show answer

(a) 0.00500 mol

(b) 0.00500 mol

Common mistakes: Not converting volume to dm³; Using incorrect stoichiometric ratio

Show mark scheme and worked solution

Marking points

M1 (a) · 1 mark · Calculates moles of KOH using concentration × volume/1000 (0.200 × 25.0/1000)

M2 (b) · 1 mark · Calculates moles of HNO3 using concentration × volume/1000 (0.200 × 25.0/1000)

B1 (c) · 1 mark · States the correct simplest whole-number ratio is 1:1 as shown in the balanced equation.

Worked solution

a) Number of moles of KOH:

b) Number of moles of HNO₃:

c) The balanced equation shows a 1:1 ratio between KOH and HNO₃, so the ratio is 1:1.