Question

1. Using your determined value of K_sp, calculate how many milligrams of Ag₂CrO₄ will dissolve in 10.0 mL of H₂O.

K_sp=8.26*10^-11.

2. Use your K_sp and show, by calculation, that Ag₂CrO₄ should precipitate when 5mL of 0.004M AgNO₃ are added to 5mL of 0.0024M K₂CrO₄.

K_sp=8.26*10^-11

Please show work on both.

Answer 1

Q1 Using your determined value of Ksp, calculate how many milligrams of Ag2CrO4 will dissolve in 10.0 mL of H2O. Ksp=8.26*10-11

Solution :-

Dissociation equation for the Ag2CrO4 is as follows

Ag2CrO4   ----- > 2 Ag^+   + CrO4^2-

                             2x                 x

Ksp euation is as follows

Ksp = [Ag^+]²[CrO4^2-]

Now lets calculate the molar solubility of the Ag2CrO4 using the ksp value.

8.26*10^-11 = [2x]²[x]

8.26*10^-11 = 4x³

8.26*10^-11/4 =x³

2.07*10^-11 = x³

By taking cube root of both sides we get

2.74*10^-4 =x

Therefore the molar solubility if the Ag2CrO4 is 2.74*10^-4 mol per liter

We have to find mass of the Ag2CrO4 in 10 ml water sample

10 ml * 1 L / 1000 ml = 0.010 L

Now lets calculate the moles of the Ag2CrO4 that are soluble in 10 ml water

Moles = molarity * volume in liter

Moles if Ag2CrO4 = 2.74*10^-4 mol per L * 0.010 L

                                 = 2.74*10^-6 mol

Now lets convert the moles of Ag2CrO4 to its mass

(2.74*10^-6 mol * 331.7301 g / 1 mol Ag2CrO4)* (1kg / 1000 g) =9.1*10^-7 kg

Therefore mass of the Ag2CrO4 that can be soluble in 10 ml water is =9.1*10^-7 kg

Q2 Use your Ksp and show, by calculation, that Ag2CrO4 should precipitate when 5mL of 0.004M AgNO3 are added to 5mL of 0.0024M K2CrO4. Ksp=8.26*10-11

Solution :-

Lets find the final concentration of the each AgNO3 and K2CrO4 after mixing the solutions

The final volume of the solution after mixing = 5 ml + 5ml = 10 ml

Final concentration of the AgNO3 = 0.004 M * 5 ml / 10 ml = 0.002 M

Final concentration of the K2CrO4 =0.0024 M * 5 ml / 10 ml = 0.0012 M

Now lets calculate the reaction quotient (Qc) and compare it with Kc

Qc= [Ag^+]²[CrO4^2-]

Lets put the concentration values in the formula.

Qc =[0.002]²[0.0012]

Qc = 4.8*10^-9

Qc > Kc therefore Ag2CrO4 will precipitate out.