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1) If the reaction NH 3 (aq)+ H 2 O(l) = NH 4 + (aq) + OH - (aq) has a reaction

ID: 815784 • Letter: 1

Question

1) If the reaction NH3(aq)+ H2O(l) = NH4+(aq) + OH-(aq) has a reaction equilibrium constant of 1.80x10-5, then what is the equilibrium constant be for NH4+ (aq) = NH3(aq) + H+(aq)? Show work. A) 1.8E-19 B) 5.6E-10 C) 1.8E-15 D) 5.6E-4

2) Phosphorus pentachloride gas decomposes to form phosphorus trichloride gas and chlorine gas. What is the equilibrium constant for this reaction if a reaction vessel has an initial concentration of phosphorus pentachloride of 1.60 M and the equilibrium concentration of 0.680 M?

1) If the reaction NH3(aq)+ H2O(l) = NH4+(aq) + OH-(aq) has a reaction equilibrium constant of 1.80x10-5, then what is the equilibrium constant be for NH4+ (aq) = NH3(aq) + H+(aq)? Show work. A) 1.8E-19 B) 5.6E-10 C) 1.8E-15 D) 5.6E-4

2) Phosphorus pentachloride gas decomposes to form phosphorus trichloride gas and chlorine gas. What is the equilibrium constant for this reaction if a reaction vessel has an initial concentration of phosphorus pentachloride of 1.60 M and the equilibrium concentration of 0.680 M?

Explanation / Answer

1)

NH3(aq)+ H2O(l) = NH4+(aq) + OH-(aq)  

The equilibrium constant kb= 1.80 x 10^-5

NH4+ (aq) = NH3(aq) + H+(aq)

This reaction is the reverse of the first reaction.

So, equilibrium constant for reverse reaction is ka = Kw / Kb

ka = (1 x 10^-14) / (1.80x10-5) = 5.56 x 10^-10

Ka = 5.6 x 10^-10

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2)

          PCl5(g) <--------------->   PCl3(g)   + Cl2(g)

I         1.60                               0                  0

C         -x                            +x              +x

E        1.60-x                       +x              +x

But given equilibrium concentration of PCl5 = 0.680 = 1.60 - x

Thus, x = 1.60 - 0.680 = 0.920 M

[Cl2] = 0.920 M

[PCl3] = 0.920

[PCl5] = 0.680

Kc = [Cl2][PCl3] / [PCl5]

Kc = (0.920)^2 / 0.680

Kc = 1.24