The chloride content of blood serum, cerebrospinal fluid or urine can be measure

ID: 781235 • Letter: T

Question

The chloride content of blood serum, cerebrospinal fluid or urine can be measured

by titration of the chloride with mercuric ion: Hg2+ + 2Cl---> HgCl2(aq). When

the reaction is complete, excess Hg2+ reacts with the indicator,

diphenylcarbazone, which forms a violet-blue color.

(a) Mercuric nitrate was standardized by titrating a solution containing 147.6

mg of NaCl, which required 28.06 mL of Hg(NO3)

2 solution. Find the

molarity of the Hg(NO3)

(b) When this same Hg(NO3)

2 solution was used to titrate 2.000 mL of urine,

22.83 mL was required. Find the concentration of Cl-

(mg/mL) in the

urine.

(a) Mass of NaCl = 147.6*(10^ -3) g

Moles of NaCl = 147.6*(10^ -3)/58.5 = 2.52*(10^ -3)

Moles of Hg required = 1/2* 2.52*(10^ -3) = 1.26*(10^ -3)

Volume = 0.02806

Moles of Hg = M*V = M*(0.02806)

Molarity = 1.26*(10^ -3)/(0.02806) = 4.49*(10^-2) = 0.045 M

(b) Molarity = 0.045

Volume = 22.83 ml = 0.02283 L

Volume of Urine = 2 ml = 0.002 L

Molarity of Urine = (0.045)*(0.02283)/(0.002)

= 0.513 M

So concentration Of Cl- = 0.513 mg/ml

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