Result

Table: Shows the absorbance value of different solution at pH1.

Solution Volume of Salicylic acid (ml) Volume of pH 1 buffer solution (ml) Absorbance

A 25 25 0.508

B 20 30 0.415

C 15 35 0.193

D 10 40 0.189

E 5 45 0.088

X (unknown) 0.534

Table: Shows the absorbance value of different solution at pH8.

Solution Volume of Salicylic acid (ml) Volume of pH 8 buffer solution(ml) Absorbance

A 25 25 0.370

B 20 30 0.298

C 15 35 0.214

D 10 40 0.138

E 5 45 0.066

X (unknown) 0.903

Calculation

Stock solution of Sodium Salicylate is 0.0005% (w/v) = 0.005g/100ml

Convert this into a molar concentration, using the following equation:

Molarity (M) = Fraction of 1L x (weight (g))/MW

= 1000/100 x 0.005/160.1

= 0.000312 M

Now, to calculate the concentration of the standards using: C1V1 = C2V2

Where,

C1 = concentration of the stock solution of sodium salicylate, 0.000312M as calculated above. This case C1 is kept the same throughout each calculation.

V1 = the volume of stock solution of salicylic acid, which would be different for each calculation being either 25, 20, 15, 10 or 5 cm3

C2 = the concentration of stock solution of salicylic acid

V2 = the total volume which is 50 cm3. This is kept constant throughout each calculation.

Solution A

C1=0.000312M V1=25 C2=? V2=50

Table: Shows the absorbance value of different solution at pH1.

Solution Volume of Salicylic acid (ml) Volume of pH 1 buffer solution (ml) Absorbance

A 25 25 0.508

B 20 30 0.415

C 15 35 0.193

D 10 40 0.189

E 5 45 0.088

X (unknown) 0.534

Table: Shows the absorbance value of different solution at pH8.

Solution Volume of Salicylic acid (ml) Volume of pH 8 buffer solution(ml) Absorbance

A 25 25 0.370

B 20 30 0.298

C 15 35 0.214

D 10 40 0.138

E 5 45 0.066

X (unknown) 0.903

Calculation

Stock solution of Sodium Salicylate is 0.0005% (w/v) = 0.005g/100ml

Convert this into a molar concentration, using the following equation:

Molarity (M) = Fraction of 1L x (weight (g))/MW

= 1000/100 x 0.005/160.1

= 0.000312 M

Now, to calculate the concentration of the standards using: C1V1 = C2V2

Where,

C1 = concentration of the stock solution of sodium salicylate, 0.000312M as calculated above. This case C1 is kept the same throughout each calculation.

V1 = the volume of stock solution of salicylic acid, which would be different for each calculation being either 25, 20, 15, 10 or 5 cm3

C2 = the concentration of stock solution of salicylic acid

V2 = the total volume which is 50 cm3. This is kept constant throughout each calculation.

Solution A

C1=0.000312M V1=25 C2=? V2=50