Question

The calibration plot (Absorbance of Cu+2 vs Cu+2 concentration (mol/L)) is: A= 4.685x +0.0363

Consider CuCl2. xH2O. The mass of CuCl2. xH2O used to prepare the solution is 0.195 g and the mass of the solution is 8.987 g. The density of the solution is determined to be 0.998 g/mL.

a.) calculate the volume of the solution in L.

b.) If the solution has an absorbance of 0.632, calculate the concentration of Cu+2 in the prepared solution

c.) calculate the moled of CuCl2 in the solution

d.) calculate the mass of CuCl2 in the solution

e.) calculate the mass of H2O in CuCl2. xH2O

f.) calculate x in CuCl2. xH2O

Answer 1

Given,

Calibration point: A= 4.685x+ 0.0363

Here, A is absorbance and x is concentration.

Mass of Cucl2.XH20 = 0.195 g

Mass of solution= 8.987 g

Density of solution= 0.998 g/ml

Now, density= mass/volume

0.998= 8.987/x

x= 9 ml = 0.009 L

Also, given A= 0.632

Therefore, 0.632= 4.685x+ 0.0363

x= 0.127 M

Now, moles of Cucl2= Volume of solution× concentration of solution.

Moles= .009× .127

= 0.001143 moles.

Mass of Cucl2= moles of Cucl2× Molar mass of Cucl2.

Molar mass of Cucl2= 134.5 g/mol

So, mass of Cucl2= 0.001143× 134.5 g

=0.153 g

Also, mass of H20 in Cucl2.xH20 = mass of Cucl2.xH20 - mass of Cucl2.

Mass of H20= 0.195- 0.153 g

= 0.042 g