Question

If I pour 10ml of 0.5M Co(No3)2 stock solution in to a sample vial and use it to make up 4 different solutions ranging in concentration from 0.025M to 0.1M by pippetting 500, 1000, 1500 and 2000 micro-litres in to separate vials and making up to 10ml with of deionised water, what are the concentrations of each?

Answer 1

It is better to use table for answering this question:

- 1 micro-litres = 1.0 × 10⁻⁶ l

- Amount is given concentration multiplied by volume in litres:

$$n = CV, C \text{ is } 0.5M$$

- New concentration is amount multiplied by 1000 ml (one litre) / 10 ml