# Scientific calculations

## Explanation

Molarity-

Molarity describes the amount of particles within a substance. For example, If I had a 2L solution of 2M Hydrochloric acid (HCL) I know that I would have 6.02214076x1023 particles of HCL in in each litre.

6.02214076x1023 This number is known as Avadros number and it is a constant which describes how many particles of a substance is within a volume. This can be used to determine the concentration of a solution.

Example;

If we have 2 moles of sodium hydroxide (NaOH) there would be 6.02214076x1023 x2 in the solution.

Dilutions-

Dilutions are the bread and butter of a scientists work and are needed in most practical experiments for reagents and test samples. To calculate this there is a simple equation which can be used. The great thing about the equation is it works for any units as long as you keep constant and use the same units on each side of the equation.

At the bottom of this section an excel spread sheet can be found which has a calculator for working out serial dilutions.

Equation;

C1 x V1 = C2 x V2

Example;

If you had a 2 molar solution of NaOH and you transfer 1L of the solution into a 5L flask and fill with water what is the new concentration.

C1 = 2 (the concentration of the solution prior to dilution

C2 = 1 (the volume prior to dilution)

V1 = 5L (the dilution volume)

V2 = ? (The currently unknown value)

C1 x C2 / V1 = V2

1 x 2 / 5 = 0.4

0.4M is the new concentration after dilution.