1. Initially, only A and B are present, each at 2.00 M . What is the final conce

Question

1. Initially, only A and B are present, each at 2.00 M. What is the final concentration of A once equilibrium is reached? Express your answer to two significant figures and include the appropriate units.

2. What is the final concentration of D at equilibrium if the initial concentrations are [A] = 1.00M and [B] = 2.00M ?Express your answer to two significant figures and include the appropriate units.

3. Consider the following reaction:
NH4HS(s)?NH3(g)+H2S(g)
An equilibrium mixture of this reaction at a certain temperature was found to have [NH3]= 0.280M and [H2S]= 0.355M . What is the value of the equilibrium constant (Kc) at this temperature?

4. Use the data below to find the equilibrium constant (Kc) for the reaction A(g)?2B(g)+C(g).
A(g)?2X(g)+C(g)Kc= 0.75
B(g)?X(g)Kc= 23.4

Explanation / Answer

1 & 2)

The reverse chemical rxn A + B <--> C + D
has the following equilibrium constant
Kc = ([C] [D]) / ([A] [B]) = 6.8

The "REVERSIBLE" chemical reaction-
A + B <--> C + D
Kc = [C][D] / [A][B] = 6.8
Concentration at the start and after equilibrium-
[A] = 2.00 M --> (2.00 - X) M
[B] = 2.00 M --> (2.00 - X) M
[C] = 0.00 M --> X M
[D] = 0.00 M --> X M
6.8 = X^2 / (2.00 - X)^2
take the square root of both sides-
2.6077 = X / (2.00 - X)
5.2154 - 2.6077 X = X
5.2154 = 3.6077 X
X = 1.4456
at equilibrium-
[A] = 0.55 M
[B] = 0.55 M
[C] = 1.45 M
[D] = 1.45 M

3)
kc = [0.280][0.355] = 0.0994

4)
A(g)?2X(g)+C(g)............ Kc= [X]^2 [C] / [A] = 0.75 that means [C] / [A] = 0.75 /[X]^2

B(g)?X(g).......................Kc= [X]/[B] = 23.4 that means [X] = [B]* 23.4

A(g)?2B(g)+C(g)...... Kc = [B]^2 [C] / [A] = [B]^2 * 0.75 /[X]^2 =[B]^2 * 0.75 / {[B] * 23.4}^2 = 1.36*10^-3

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.