Question

The reaction between carbon tetrachloride, CCl4, and water, H2O, to form carbon dioxide, CO2, and hydrogen chloride, HCl, has a ?G? value of ?232 kJ/mole, and so is thermodynamically favored. But when you mix carbon tetrachloride with water, no change is observed. What is a possible explanation for this?
a) It is a slow reaction kinetically.
b) The activation energy of the reaction is too small.
c) The reaction is not spontaneous.
d)The reaction is not favored thermodynamically

2)You have some propene , H2C=CHCH3, in a compressed gas tank that you need to convert to propane,H3CCH2CH3, to run your cabin heater and fridge. You have another tank of compressed hydrogen gas, H2, sitting out in your shed. Your first idea is to fill up a third tank with a mixture of the two gases, but when you try that, nothing happens. You look under your kitchen sink and find some powdered palladium mixed in inert charcoal. You take the palladium and put it into the flowpath from the hydrogen and propene tanks. As you begin flowing the mixture of propene and hydrogen, you notice with glee that by the time the gas reaches the receiving tank, it is propane gas. After all the propene has been converted to propane, you pour the palladium-charcoal mixture into a crucible. After analyzing the palladium, you notice that its chemical state has not changed.

Q) What word best describes the role that the palladium plays in the reaction between propene and hydrogen above?

a)It is a catalyst.

b)It is an activation energy barrier.

c)It is a solvent.

d) It is a reagent.

3) What did the palladium do to to increase the rate of the reaction between the propene and hydrogen?

a)It changed the thermodynamic equilibrium.

b)It made the Gibbs free energy of the reaction more positive.

c)It lowered the activation energy of the reaction.

d)It increased the activation energy of the reaction.

Answer 1

Answer:

1) a) It is a slow reaction kinetically.

2) a) It is a catalyst.

3) c) It lowered the activation energy of the reaction.

Explanation:

1) The reaction between carbon tetrachloride, CCl₄, and water, H₂O, to form carbon dioxide, CO₂, and hydrogen chloride, HCl, has a ΔG° value of -232 kJ/mole, and so is thermodynamically favored. But when you mix carbon tetrachloride with water, no change is observed. What is a possible explanation for this?

a) It is a slow reaction kinetically.  TRUE. This is the most likely explanation of why no change is observed.

b) The activation energy of the reaction is too small.  FALSE. Slow reactions have a large activation energy.

c) The reaction is not spontaneous. FALSE. ΔG° < 0 so the reaction is spontaneous.

d)The reaction is not favored thermodynamically. FALSE. ΔG° < 0 so the reaction is favored thermodynamically.

2) What word best describes the role that the palladium plays in the reaction between propene and hydrogen above?

It is a catalyst because it increases the rate of the reaction without being altered by the end of the reaction.

3) What did the palladium do to increase the rate of the reaction between the propene and hydrogen?

a)It changed the thermodynamic equilibrium.  FALSE. Catalysts don't affect equilibrium

b)It made the Gibbs free energy of the reaction more positive.  FALSE. Catalysts don't affect Gibbs free energy.

c)It lowered the activation energy of the reaction.  TRUE. According to the Arrhenius equation, the lower the activation energy, the higher the rate constant, and the higher the rate of reaction. This is how catalysts act.

d)It increased the activation energy of the reaction. FALSE.