# The purity of aminosulphonic acid

Titration number

1

2

3

4

23.30

22.50

45.10

23.50

0.00

0.10

22.40

1.00

Amount of acid used for each titration:

1- 23.00-0.00=23.00 cm3

2- 22.50-0.10=22.40 cm3

3- 45.10-22.40=22.70 cm3

4- 23.50-1.00=22.50 cm3

The amount of acid used for the first titration is a little higher than it should be so to make the calculation much more accuracy I will ignore the first one and I will work out the average of the other three values:

22.40+22.70+22.50=67.6 cm3

67.6/3=22.53 cm3 (2 decimals place)

22.53 cm3 is average amount of acid (H2NSO3H) reacted with 25.00 cm3 of alkali (NaOH) with concentration of 0.200 moldm-3.

Now I am going to work out the number of moles of NaOH in 25.00 cm3 of that with concentration of 0.200 moldm-3:

CV=M

C=0.200 moldm-3 M=0.200*25.00/1000=0.005 number of moles of NaOH

V=25.00 cm3 reacted with acid.

M=number of moles

As the ratio of the acid to the alkali in the reaction is 1-1 so number of moles of the acid reacted with the alkali are as same as number of moles of the alkali reacted with the acid because of ratio of 1-1.

Now I can say that the number of moles of acid in 22.53 cm3 of that (which is the average amount of the acid I worked that out before) is equal to 0.005. So I can work out the number of moles of acid in 250cm3 of that.

Number of moles in cm3 X=250*0.005/22.53

0.005 22.53 X=0.0555 moles in 250 cm3 acid

X 250

Now I can work out the number of grams of the acid (H2NSO3H) by using its molecular number (Mr=97):

Number of moles of H2NSO3H is equal to this number of grams

1 97

0.0555 Y

Y=0.0555*97=5.3835 grams

Now I can work out the value of percentage purity which is :

Percentage purity = 5.3835/5.6=0.9613=96.13%

Also I can work out the value of percentage error in the result which is:

% Error in the result = (99.1-96.13)*(100/99.1)= 2.99=2.99%

Now I am going to estimate the maximum percentage error in using each piece of apparatus, and the overall percentage error.

Balance= +/-0.1g = (0.1/5.6)

25cm3 pipette = +/-0.05cm3 = (0.05/25)

Burette = +/- 0.10cm3 = (0.10/22.53)

The overall value of error is sum of the above numbers which is:

Overall error = (0.1/5.6) + (0.25/250) + (0.05/25) + (0.10/22.53) = 0.0253=2.53%

Reasons for the values of errors and differences in each step could be: