The standard calculation

3 marks · Easy

A student is titrating 25.0 cm³ of sodium hydroxide solution with hydrochloric acid. The concentration of sodium hydroxide is 0.200 mol/dm³.

(a)

Calculate the number of moles of sodium hydroxide in 25.0 cm³.

[2 marks]

(b)

State the equation you would use for this calculation.

[1 mark]

(c)

Give the unit for the concentration used in the calculation.

[0 marks]

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(a) 0.00500 mol

(b) number of moles = (volume in dm³) × (concentration in mol/dm³)

Show mark scheme and worked solution

Marking points

M1 (a) · 1 mark · Converts 25.0 cm³ to 0.0250 dm³ or correctly sets up the calculation. (follow-through allowed) (follow-through)

A1 (a) · 1 mark · Calculates correct number of moles: 0.00500 mol. (follow-through)

B1 (b) · 1 mark · States the correct equation used: number of moles = volume (dm³) × concentration (mol/dm³).

Worked solution

a) Convert volume to dm³: 25.0 cm³ = 0.0250 dm³

b) The equation is: number of moles = volume (dm³) × concentration (mol/dm³)

c) The unit for concentration is mol/dm³.