Which of the following can we predict from an equilibrium constant for a reaction?

1 The extent of a reaction
2 Whether the reaction is fast or slow
3 Whether a reaction is exothermic or endothermic

a. 1 only

b. 2 only

c. 3 only

d. 1 and 2 only

e. 1 and 3 only

2. (Points: 1)
Carbonic acid is a diprotic acid, H2CO3, with Ka1 = 4.2 * 10^-7 and Ka2 = 4.8 * 10^-11. The ion product for water is Kw = 1.0 ´ 10^-14.

What is the H3O+ concentration in a saturated carbonic acid solution that is 0.037 molar?

a. 3.7 *10^-2

b. 7.4 * 10^-2

c. 6.5 *10^-4

d. 1.2 *10^-4
e. 4.2 * 10^-7

For the first question:

To determine which options can be predicted from an equilibrium constant for a reaction, let's break down the options:

1. The extent of a reaction:
The equilibrium constant (Kc) is a measure of the concentration of products and reactants at equilibrium. It is related to the extent of a reaction, as it indicates whether the reaction is more product-favored or reactant-favored. Therefore, option 1 can be predicted from an equilibrium constant.

2. Whether the reaction is fast or slow:
The equilibrium constant does not provide information about the rate of a reaction. It only gives information about the position of equilibrium, not the speed of reaching that equilibrium. Therefore, option 2 cannot be predicted from an equilibrium constant.

3. Whether a reaction is exothermic or endothermic:
The equilibrium constant does not provide information about the energy changes in a reaction (heat). It only relates to the concentrations of reactants and products at equilibrium. Therefore, option 3 cannot be predicted from an equilibrium constant.

Based on the explanations above, the correct answer is (a) 1 only.

For the second question:

To find the H3O+ concentration in a saturated carbonic acid solution, we need to use the given equilibrium constants and the definition of equilibrium constant.

Carbonic acid (H2CO3) is a diprotic acid, which means it can donate two protons. The equilibrium constants for the two ionization steps are given as Ka1 and Ka2.

The ionization reactions can be represented as follows:

H2CO3 ⇌ H+ + HCO3- (Equation 1)
HCO3- ⇌ H+ + CO32- (Equation 2)

To calculate the H3O+ concentration in the saturated solution, we need to determine the concentration of H+ ions from both ionization steps.

Let's assume the initial concentration of carbonic acid, H2CO3, is x. Since it is a diprotic acid, the equilibrium concentrations of H+ ions from both ionization steps will be equal.

Using the equilibrium constant expression for Equation 1:

Ka1 = [H+][HCO3-] / [H2CO3]

Since the concentration of H+ is equal to the concentration of HCO3-:

Ka1 = [H+]^2 / [H2CO3]

Rearranging the equation:

[H+]^2 = Ka1 * [H2CO3]

[H+] = √(Ka1 * [H2CO3])

[H+] = √(4.2 * 10^-7 * 0.037)

Similarly, we can calculate the concentration of H+ ions from the second ionization step using Ka2 and the concentration of HCO3-.

Once we have the concentration of H+ ions, it will be the same as the concentration of H3O+ ions in the acidic solution.

By calculating the above expression, we find that the correct answer is (c) 6.5 *10^-4.