Lecture 2MeasurementsConcentration

Solution Preparation

Density kg/L = g/mL

Density of water @4o C 1.00 g/mL

Specific gravity = density /(density of water @4o C)

Dimensionless!

For diluted aqueous solutions, 1 kg 1 L

Solutions

%% ‘per cent’ 10g/1000gor 10g/L

ppm ‘part per million’

0.01 10-2

1/1,000,000 10-6

10g/kg

(10-6g = 1 g)

1 g/gor 1 mg/L1 g/mL

1 mg/kg

ppb ‘part per billion’

10-9 (10-9g = 1 ng)

1 ng/gor 1 g/L1 ng/mL

1 g/kg

ppt - parts per thousand or parts per trillion!?

Molarity mole/L

Molecular mass, formula mass.Molecular weight, formula weight FW grams!

Molarity 10 (X %) / FW

Example: 1% HCl

FW = 1+35.5=36.5 Molarity(1%HCl)= 10/36.5=0.27 M

Molarity = 0.001(X ppm) / FWExample: 10 ppm PbFW=207.2

Molarity(10ppm Pb)= 10-3 10/207.2=4.8210-5 M

In diluted aqueous solutions:

Dilution

afterbefore molesofnumbermolesofnumber ____

beforebeforebefore ionconcentratvolumemolesofnumber __

afterafterafter ionconcentratvolumemolesofnumber __

afterafterbeforebefore ionconcentratvolumeionconcentratvolume

10 mL200 ppm = 200 mL 10 ppm

To make 200 mL of 10 ppm solution from 200 ppm , take 10 mL and dilute to the volume of 200 mL

5 mL0.400 M = 100 mL 0.020 MTo make 100 mL of 0.02M solution from 0.40 M , take 5 mL and dilute to the volume of 100 mL

C1 V1 = C2 V2