Question

The standard curve generated from his data is y=16.943x+0.0077 (absorbance on the y-axis and concentration on the x-axis

• Mass of unknown nickel salt he used to prepare 25 mL of solution: 0.2755g.

• Absorbance reading of unknown nickel salt solution (at appropriate wavelength): 0.436. Calculate the mass% of Sulfate.

Please show work

Answer 1

Absorbance for unknown sample is 0.436. When we put this value as x in the equation given, we can find x.

0.436 = 16.943x+0.0077

x = 0.0253 M

Concentration is coming out to be 0.0253 M

But the concentration prepared was:

volume = 25 ml = 0.025 L

mass = 0.2755 g

Molar mass of nickel sulfate = 154.75 g/mol

Molarity = mass/(molar mass*volume) = 0.2755/(154.75*.025) = 0.0712 M

Mass % of sulfate = (concentration from absorbance/concentration prepared)*100

= (0.0253/0.0712)*100 = 35.53 %

Mass % of sulfate = 35.53 %