Question

I need help with questions 3 and 4!!

3. Calculate the normality of the silver nitrate solution and percent chloride in the sample: 352.4 mg pure KCl require 48.33 ml AgNO3 solution 323.3 mg of unknown requires 32.02 ml AgNO3 solution Calculate the titration error. 4. A sample of silver alloy weighing 984.6 mg was dissolved in nitric acid. The solution was neutralized, and 252.2 mg of pure NaCl added. The excess chloride required 19.09 ml of 0.0935 N AgNO3 in a Mohr titration. What is the percent silver in the alloy?

Answer 1

3) molecular weight of KCl = 74.55 g/mol

molecular weight of AgNO3 = 169.87 g/mol

352.4 mg KCl = 4.73*10^-3 mol

reaction of AgNO3 and KCl : AgNO3 + KCl ------> AgCl + KNO3

so 1 mole of KCl reacts with 1mole AgNO3

so moles of AgNO3 = 4.73*10^-3 mole

Normality of silver nitrate solution = 4.73*10^-3/0.04833 = 0.098 N

In the 323.3 mg unknown sample 32.02 ml of 0.098 N AgNO3 solution required

moles of chloride in unknown sample = 0.098*0.03202 = 3.14*10^-3 mole

percent chloride = 3.14*10^-3*35.45*100/0.3233 = 34.43%

4) weight of alloy = 984.6 mg = 0.9846 g

252.2 mg NaCl = 0.2522/58.44 = 4.31*10^-3 mole

excess chloride in sample = 1.78*10^-3

chloride reacted with silver = 2.53*10^-3 mole

weight of silver = 2.53*10^-3*107.87 = 0.2729 g

percent silver = 0.2729/0.9846*100 = 27.72%