UNIT11PracticeTest Page12of13
Equilibrium
The only reaction that has equivalent moles of gas on both sides of the reaction is response A. Therefore, it will not
be affected by altering the pressure.
18. D
In order to increase the number of CS
2
moles, the equilibrium reaction must be stressed so that it causes a shift toward
the CS
2
, which is on the product’s side. This can be caused by removing the other product (Cl
2
), by increasing the
temperature for this endothermic reaction, and by decreasing the pressure/ increasing the volume of the system. The
only response that follows one of these stresses is response D.
Notice that altering the quantities of reactants (as in responses A or B) does not cause any shift, since the reactants do
not have concentrations, as they are liquids.
19. C
The “yield,” remember, means the creation of products. Therefore, the equilibrium reaction must be stressed so that it
shifts to the product’s side. This can be caused by adding more reactant or by increasing the temperature for this
endothermic reaction. The only response that follows one of these stresses is response C.
Notice that altering the pressure of this reaction (as in responses A or B, or similarly by response E) does not cause
any shift, since there are 6 moles of gaseous reactants and 6 moles of gaseous products.
20. E
Reactions that involve gases tend to be affected by pressure changes, while reactions that do not have any gases will
definitively not be affected by pressure changes. The same is true of volume changes. Notice that no reaction is
entirely void of gases.
Reactions that involved gases with equivalent moles of gas on both sides of the reaction will have rates equally
affected by a volume change. So look at how many gaseous particles appear on each side of the reactions:
Response A: 3 gaseous reactants to 2 gaseous products
Response B: 2 gaseous reactants to 1 gaseous product
Response C: 5 gaseous reactants to 2 gaseous products
Response D: 2 gaseous reactants to 0 gaseous products
Response E: 2 gaseous reactants to 2 gaseous products
The only reaction that has equivalent moles of gas on both sides of the reaction is response E. Therefore, it will not
be
affected by altering the volume.
21. C
First, notice that the first reaction presented has the same temperature as the second reaction. Next, compare the
second reaction to the first reaction.
The second reaction is reversed, compared to the first reaction. This means that the new K value will be the inverse of
the original K value.
The second reaction is also ½ the coefficients of the first reaction. This means that the new K value will be the square
root of the original K value.
Putting this all together,
11
0.134
55
new
old
K
K
22. A
Reactions that involve gases tend to be affected by volume changes. If a decrease in volume causes a shift to the
right, the number of gaseous particles on the right side of the reaction must be lower than the number of gaseous
particles on the left side. So look at how many gaseous particles appear on each side of the reactions:
Response A: 4 gaseous reactants to 2 gaseous products
Response B: 2 gaseous reactants to 3 gaseous productx
Response C: 2 gaseous reactants to 3 gaseous products
Response D: 0 gaseous reactants to 2 gaseous products
Response E: 2 gaseous reactants to 2 gaseous products