Help please I\'ve gotten this wrong so many times For the following questions, i

Question

Help please I've gotten this wrong so many times

For the following questions, identify the ions comprising the salt, and then use the expression for the solubility product to perform the necessary calculations. This simple exercise involves the assumptions that you can ignore any complications which might result as a consequence of the basicity or acidity of the ions, ion pairing, complex ion formation, or auto-ionization of water.

Calculate the concentration, in mol/L, of a saturated aqueous solution of Ca5(PO4)3OH (Ksp = 6.80×10-37).

mol/L
1 pts

Calculate the solubility, in g/100mL, of Ca5(PO4)3OH.

g/100mL
1 pts

Calculate the mass of AgCl (Ksp = 1.60×10-10) which will dissolve in 100 ml of water.

1 pts

Explanation / Answer

we know that

Ca5(P04)3OH ---> 5 Ca+2 + 3 P043- + OH-

let the molar solubility be s

then

[Ca+2] = 5s

[P043-] = 3s

[OH-] = s

now

Ksp = [Ca+2]^5 [P043-]^3 [OH-]

Ksp = [5s]^5 [3s]^3 [s]

Ksp = 8435 x s^9

so

8435 x s^9 = 6.8 x 10-37

s = 2.7166 x 10-5

so

the molar solubility (mol/L) is 2.7166 x 10-5

2)

now

solubility in g / L = solubility in mol / L x molar mass

so

solubility in g / L = 2.7166 x 10-5 x 502.1

solubility in g / L = 0.01364

solubility in g / ml = solubility in g/ L / 1000

solubility in g / ml = 0.01364 / 1000 = 1.364 x 10-5

solubility in g / 100 ml = 1.364 x 10-5 x 100 = 1.364 x 10-3

so

solubility in g / 100 ml is 1.364 x 10-3

3)

AgCl --> Ag+ + Cl-

let the molar solubility be s

then

[Ag+] = s

[CL-] = s

now

Ksp = [Ag+] [Cl-]

Ksp = [s] [s]

Ksp = s2

s2 = 1.6 x 10-10

s = 1.2649 x 10-5

so

the molar solubility in mol / L is 1.2649 x 10-5

now

solubility in g / L = molar solubility x molar mass

solubility in g/ L = 1.2649 x 10-5 x 143.32 = 1.81287 x 10-3

now

solubility in g / ml = 1.81287 x 10-3 / 1000 = 1.81287 x 10-6

now

for 100 ml

amount of AgCl = 1.81287 x 10-6 x 100

amount of AgCl = 1.81287 x 10-4

so

1.81287 x 10-4 grams of AgCl will dissolve in 100 ml

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