Question

a 0.275 M solution of Cu2+ gives an absorbance reading of 0.788 at 620 nm. another solution gives an absorbance reading of 0.340 under the same conditions. what is the concentration of the second solution in moles of Cu2+/L and grams of Cu2+/L?

Answer 1

Concerntration of the 1st compound = 0.275 M

Absorbance of the 1st compound = 0.788

Conc. of the 2nd compound = ?

Absorbance of the 2nd compound = 0.340

We know from the Beer Lambart's Law

A = * c * l

Where A= Absorbance

c= Conc. of the sample

l = Length of the sample

= Constant

So A1 / A2 = c1 / c2

as all other parameters remains the same

So 0.788 / 0.340 = 0.275 / c2

=> c2 = 0.1186 M

concentration of the second solution in moles of Cu2+/L = 0.1186 moles / Litre

concentration of the second solution grams of Cu2+/L = 0.1186 * 63.55 /lit

=  7.53 gm / Lit