Question

5.00mL of a Co+2 solution gives absorbance, A, of 0.50 at its lamda max using an...

5.00mL of a Co+2 solution gives absorbance, A, of 0.50 at its lamda max using an UV-visible spectrophotometer. If 5.00mL of 0.100M Co2+ solution is added into this Co2+ solution, the absorbance is 0.75. Calculate the concentration of Co2+ in the previous (original) solution.

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Homework Answers

Answer #1

0.050M

Explanation

Soriginal/Soriginal + std = Coriginal / ((Coriginal + Cstd)/dilution factor)

where,

Soriginal = Absorbance for original , 0.50

Soriginal + std = Absorbance for std added solution ,0.75M

Coriginal = Original solution concentrstion,?

Cstd = 0.100M

substitute the values

0.50/0.75 = Coriginal /(0.100M + (Corigina)/2 )

(0.05M + (0.5Coriginal))0.6667 = Coriginal

  0.0333M+ 0.6667(0.5Coriginal) = Coriginal

0.6667Coriginal = 0.0333M

Coriginal = 0.050 M

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