Concentration

Concentration

V

nc

Particles per volume

Can be in grams per litre but chemists usually express concentration in moles per litre

This are related by the formula:

Where:n = molesV = volume in litresc = concentration in molL-1

Write the formula for:

1. Moles using mass and Molar mass

2. Concentration using Volume and Moles

)Mr(gmol(g) m

n 1-

Vn

c

Concentration Example15 grams of NaCl is dissolved in 1 litre of water, what is the concentration of the solution in moles per litre? (M NaCl = 58.5 gmol-1)

Find moles of NaCl

Divide moles by volume in litres

mol 0.2564 58.515

Mm

n

1molL256.0litre 1

0.2564mol

Vn

c

Concentration Example20 grams of NaOH is dissolved in 500mls of water, what is the concentration of the solution in moles per litre? (M NaOH = 40gmol-1)

Find moles of NaOH

Divide moles by volume in litres

mol 0.5 40gmol

20g

Mm

n1-

1 00.10.5litre

0.5mol molL

V

nc

Have a go

• Calculate the concentration of 18.0g of glucose (C6H12O6) dissolved in 200ml of solution.

• n=m/Mr• n=18.0g/180gmol-1

• n=0.100mol

• c=n/V• c=0.100mol/0.200L• c=0.500molL-1