Mass of Acetylsalicylic acid in solution = .25g Standard made from 0.500mL of st

Question

Mass of Acetylsalicylic acid in solution = .25g

Standard made from 0.500mL of stock solution absorbance = .817

.400mL = .687

.300mL = .505

.200mL = .335

.1mL = .030

Absorbance of Asprin tablet = .17

1) Determine the concentration of the acetylsalicylic acid in the 100mL flask containing the solution from which the standars were made in M.

2) determine the concentration of the acetylsalicylic acid in each of the 10mL calibration solutions. this is a simple dilution - as long as you use the correct volumes.

3) Concentration of acetylsalicylic acid in 10.00 mL solution

4) Concentration of acetylsalicylic acid in 100.00 mL solution

Explanation / Answer

The molecular weight of acetylslicylic acid = 180

MAss = 0.25 g

1) Determine the concentration of the acetylsalicylic acid in the 100mL flask containing the solution from which the standars were made in M.

Solution : Concentration = mass / molecular weight x Volume in Litres = 0.25 / 180 X 0.1 = 0.0138 M

2) determine the concentration of the acetylsalicylic acid in each of the 10mL calibration solutions. this is a simple dilution - as long as you use the correct volumes.

We have used 0.500mL of stock solution

so the new concentration can be calculated from M1V1 = M2V2

0.0138 M X 0.5 mL = M2 X 10mL

M2= new concentration = 0.00069 M

(ii)

We have used 0.400mL of stock solution

so the new concentration can be calculated from M1V1 = M2V2

0.0138 M X 0.4 mL = M2 X 10mL

M2= new concentration = 0.000552 M

(iii)

We have used 0.300mL of stock solution

so the new concentration can be calculated from M1V1 = M2V2

0.0138 M X 0.3 mL = M2 X 10mL

M2= new concentration = 0.000414 M

(iv)

We have used 0.200mL of stock solution

so the new concentration can be calculated from M1V1 = M2V2

0.0138 M X 0.2 mL = M2 X 10mL

M2= new concentration = 0.000276 M

(v)

We have used 0.100mL of stock solution

so the new concentration can be calculated from M1V1 = M2V2

0.0138 M X 0.1 mL = M2 X 10mL

M2= new concentration = 0.000138 M

3) Concentration of acetylsalicylic acid in 10.00 mL solution

Will be same as above

4) Concentration of acetylsalicylic acid in 100.00 mL solution

The concentrations will be

(i) 0.000069 M

(ii)0.0000552 M

(iii) 0.0000414 M

(iv) 0.0000276 M

(v) 0.0000138 M

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