When 0.1009 g of sodium cyanide is dissolved in solution

Question

When 0.1009 g of sodium cyanide is dissolved in solution, it takes 19.22 mL of a potassium permanganate

solution to reach the end point of the titration. Using the balanced chemical equation provided, determine

the molarity of the potassium permanganate. You will be doing a similar reaction in the laboratory this

week. (Remember: the mole ratio of MnO4

- to KMnO4 is 1:1 and the mole ratio of CN- to NaCN is 1:1)

H2O (ℓ) + 2 MnO4

- (aq) + 3 CN- (aq) → 2 MnO2 (s) + 3 CNO- (aq) + 2 OH- (aq)

Answer 1

Find the moles of NaCN:

molar mass NaCN = 49.00 g / mol

0.1009 g NaCN x 1 mol NaCN / 49.00 g = 2.059x10^-3 mols

Find moles KMnO₄:

2.058x10^-3 mol NaCN x 1 mol KMnO₄ / 1 mol NaCN = 2.059x10^-3 mols

Find molarity of KMnO₄:

2.059x10^-3 mols / 19.22 ml x 1000 ml / L = 0.0171 mols / L = 0.0171 M