Question

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question 11 (1 point)
when a catalyst is added to a chemical system involving a reversible reaction, the
catalyst ______.

• increases the rate of reaction in both directions
• increases the rate of reaction in the forward direction only
• increases the rate of reaction in the reverse direction only
• has no effect on the rate of reaction in either direction
• shifts equilibrium in one direction

question 12 (1 point)
when the equilibrium constant is very small, the approximate concentration of
reactant at equilibrium is ______ the initial concentration.

• greater than
• less than
• the same as
• exactly 100 times
• exactly 1 000 times

question 13 (1 point)

Explanation:

For Question 11: A catalyst provides an alternative reaction pathway with lower activation energy. In a reversible reaction, it lowers the activation energy for both the forward and reverse reactions. So, it increases the rate of reaction in both directions. It does not shift the equilibrium (Le - Chatelier's principle; catalysts affect kinetics, not thermodynamics).
For Question 12: The equilibrium constant \(K=\frac{[products]}{[reactants]}\). If \(K\) is very small (\(K\ll1\)), then \(\frac{[products]}{[reactants]}\ll1\), which implies \([reactants]\gg[products]\). So, most of the reactants remain unreacted at equilibrium, and the approximate concentration of reactant at equilibrium is greater than the initial concentration (since only a small amount of reactants have been converted to products).

Answer:

Question 11: increases the rate of reaction in both directions
Question 12: greater than