Question #163032

20 tablets weighing 2g was powdered. Exactly 50mg was transferred to 100mL volumetric flask and diluted with water. 10mL aliquot was transferred to another 100mL and diluted to volume. The A value of the solution was 0.652 and the absorptivity value was 15mg/mL/cm. What is the mg of paracetamol per tablet from the following data? Please provide a step by step solution. Thank you.

Expert's answer

Absorption formulae:

A = a b c,

Whereby

A – absorbance (0.652)

a – absorptivity (15mg/ml/cm)

b – length of part (1cm)

c – concentration

substitution;

c = A/(ab) = 0.652/ (15mg/ml/cm x 1cm) = 0.0435mg/ml

Result;

The second 100ml volumetric flask contained 0.0435mg/ml x 100ml = 4.35mg of paracetamol.

Hence the first 100ml flask contained 4.35mg x 10 = 43.5mg of paracetamol. This means that, 50mg of tablet consists of 43.5mg of paracetamol.

Since 20 tablets weigh 2g, one tablet weighs 2g/20 =0.1g = 100mg.

Thus as 50mg of tablet contains 43.5mg of paracetamol, one tablet (100mg) contains 43.5mg x 2 =87 mg of paracetamol.

Hence the answer is 87mg

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