The following table is the absorbances measured using Flame Atomic Absorption; F

Question

The following table is the absorbances measured using Flame Atomic Absorption;

Flask

100mg/L Ca2+ solution added

A

0mL

B

0mL

C

2mL

D

5mL

E

8mL

F

10mL

G

15mL

Here is the amount of standard 100mg/L calcium solution that was added to each flask;

Flask

100mg/L Ca2+ solution added

B

0mL

C

2mL

D

5mL

E

8mL

F

10mL

G

15mL

I now need to plot the absorbance of each solution against the mass of calcium added to it, and then solve for the x-intercept to find the calciium present in the juice sample. I keep getting a negative value for my x-intercept and I think it is because I am not solving for the mass of calcium added to it correctly.

How do you solve for mass of calcium added to each solution?

Flask

100mg/L Ca2+ solution added

A

0mL

B

0mL

C

2mL

D

5mL

E

8mL

F

10mL

G

15mL

Explanation / Answer

So the mass of Calcium added or the Calcium ion concentration in each flask can be found out by following method:-

Concentration of Calcium in the stock solution= 100 mg/L

So Molarity of stock solution= (wt of calcium taken/Molecular weight)*(1000/volume)

=(0.1 g/40g)*1000/1000

=2.5 mM

1L contain 100 mg of calcium

Flask B) 0ml will have no calcium ion

C) 2 ml will have 100mg/1000ml*2 ml=0.2 mg/ L

D) 5 ml will have 100mg/1000ml*5ml = 0.5 mg/L

E) 8 ml will have 100mg/ 1000ml*8ml=0.8 mg/L

F) 10 ml will have 100 mg/1000ml*10 ml=1 mg/L

G) 15 ml will have 100mg/1000ml*15 ml=1.5 mg/L

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