2) (30 points) A sample of approximately 50% iron is dissolved in acid, in order

Question

2) (30 points) A sample of approximately 50% iron is dissolved in acid, in order for a good od analysis to take place it has to be diluted between.0040 and .006 percent. The meth chosen was to dilute in three dilutions of ten ml each. The first dilution is a 1/5, the second dilution is a 1/6 and the third dilution is a 1/4. Determine the amount of acid to add to tube 1 and how much 50% solution to add to tube 1, Determine the amount from tube 1 and the amount of acid to put in tube 2. Determine the amount of acid an the amount from tube 2 to put into tube 3. Determine the concentration of eac Are we in the proper range? h tube.

Explanation / Answer

Concentration after Dilution can be calculated using the equation as follows:

Concentration after Dilution=Concentration before Dilution*(dilution factor)

where dilution factor=Volume before dilution/Volume after dilution

Ci=initial concentration added to tube 1

1) Stock preparation:

Cs=Concentration of stock

Vs=volume of stock

2)concentration before dilution=Cs

dilution factor=1/5

So,Volume before dilution=10ml

volume after dilution=5*10=50ml

volume of acid added=50ml-10ml=40ml

concentration after dilution=Cs(1/5)

2) second dilution,

concentration before dilution=Cs/5

dilution factor=1/6

So,Volume before dilution=10ml

volume after dilution=6*10=60ml

volume of acid added=60ml-10ml=50ml

concentration after dilution=Cs(1/5)(1/6)=Cs/30

3) Third dilution,

concentration before dilution=Cs/30

dilution factor=1/4

So,Volume before dilution=10ml

volume after dilution=4*10=40ml

volume of acid added=40ml-10ml=30ml

concentration after dilution=Cs(1/30)(1/4)=Cs/120=Cs*0.008

The concentration after final dilution =0.008 times the initial concentration.So,to get the dilution of 0.004 times,the initial concentration Ci must be,

Cs*2=Ci

or,Ci=Cs/2

or, dilution factor of initial concentration=2 (which is not possible)

Vs/Vi=2

for Vs=10ml

Vi=20ml

The solution cannot be concentrated, so the dilution method is not in proper range

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