Question

1) sulfuric acid reacts with the ammonia according to the equation below. It takes 32.89 mL of a 1.50 M solution of sulfuric acid to neutralize 64.7 mL of ammonia solution. what is the molar concentrationof the ammonia solution? H2SO4 (aq) + 2 NH3 (aq)---> (NH4)2SO4 (aq)

2) A 500.0mL solution that contains silver ion is treated with excess sodium chloride soultion, producing a precpitate of silver chloride that has a mass of 45.4 mg. What mass of silver ion was present in the original 500.0 mL sample (give the mass in mg)? Ag+ (aq) + Cl- (aq) --> AgCl (s)

Answer 1

H2SO4 (aq) + 2 NH3 (aq)---> (NH4)2SO4 (aq)

1mole H2SO4=2mole NH3

M1V1/n1 = M2V2/n2

Conc.of H2SO4 =M1= 1.50M, V1=32.89mL,n1=1

Conc. of NH3, M2=?, V2=64.7mL,n2=2

M2=(M1V1n2/n1V2) = 1.50*32.89*2/1*64.7 = 1.525M

The concentration of unknown NH3 solution = 1.525M

Ag+ (aq) + Cl- (aq) --> AgCl (s)
1mole AgCl = 1mole Ag+

i.e., 143.32g of AgCl contain 107.86g of Ag+

then 45.4mg=0.0454g of AgCl contain 107.86g/mol/143.32g/mol*0.0454g =0.0341g = 34.16mg of Ag+

Mass of silver ion in original 500mL of sample = 34.16mg