[Rocker 1414]

For this first question, I would just like a yay or nay as to whether my thinking is correct or not.
1.
Solid ammonium chloride is placed in an evacuated vessel and heated until it decomposes
NH₄Cl (s)   NH₃ (g) + HCl (g)

A.
Write the equilibrium constant of K_p

Using the ICE table, NH₃ and HCl increase by "x", while NH₄ is omitted because it is a solid. So K_p = [HCl][NH₃] = x²

B.
Equilibrium is reached at a temperature of 202 deg C, and the total pressure inside the vessel is measured to be 4.40 atm. What is the numerical value of K_p at this temperature?

P_Total = P_NH3 + P_HCl
Since P_NH3 = P_HCl = 2.20 atm, then
K_p = (2.20)² = 4.84

Does this look good?

As for this second question, I'm totally lost.

2.
A saturated solution of magnesium hydroxide, Mg(OH)₂, has a magnesium ion concentration of 1.65 x 10^-4 M at 17 deg C.

A.
Write the equation and the solubility product constant expression for the reaction.


I know an ICE table is again needed, and that the concentration of MG²⁺ should be inserted for the Initial of Magnesium, but I'm not sure where to go from there. Thanks a lot for any help.

[DevaDevil]

1
A. correct
B. correct, but do not forget the units of K_p!

2. First write the reaction equation for Mg(OH)₂ dissolution

[Rocker 1414]

Thanks very much for the verification.

The reaction would be Mg(OH)₂ (aq)   Mg²⁺ (aq) + 2OH^- (aq)

So now I simply use the reaction stoichiometry to find K_sp, correct?

K_sp = [Mg²⁺][2OH^-]²

[Rocker 1414]

One more question is stumping me here.

To an empty 1.00 liter vessel is added 0.130 mole each of NH₃ and HCl at 202 deg C. How many moles of solid NH₄Cl is formed after equilibrium is established at this temperature?


Would the below method be the correct way of figuring it out?

K_p=4.84
4.84=1/[HCl]²
since [HCl]=[NH₃]
4.84= (0.130-x)²
x=0.077
Moles_NH4Cl=0.077

[AMEDIO]

no its Kp given here not Kc
so make sure u write the expression for Kp properly...