chem help

Lactic acid has the following structure:

Its Ka = 1.4 x 10-4.

1A. What are the relative acidities of the four different types of hydrogen atom in this molecule? (list highest acidity first and refer to the numbers labeling the hydrogen atoms).

1B. If you were to make a 10-10 M solution of lactic acid in water, what would the pH of the solution be?

1C. Write the correct expression for the Kof lactic acid.

2. For the reaction: N2O4(g)2 NO2(g) at 1000C, three separate experiments were carried out in identical containers. The following data were recorded:

Experiment #

[Initial]

[Equilibrium]

Value at equilibrium of the quantity

 

[N2O4]

[NO2]

[N2O4]

[NO2]

[NO2]2/ [N2O4]

1

1.00

0

0.80

0.40

X

2

Y

0

1.71

0.58

0.20

3

0

2.00

Z

0.40

0.20

Complete the table by calculating the missing values for X, Y, and Z.

3. Some ions we have studied are amphoteric, meaning they can behave as either acids or bases when added to water. One very important example is the bicarbonate ion, HCO3, which has a Ka = 5.6 x 10-11 and a Kb = 1.7 x 10-9.

4A. Write the chemical equilibrium equation that you would use to determine Ka for bicarbonate?

4B. Write the chemical equilibrium equation that you would use to determine Kb for bicarbonate?

4C. Considering the data above, will a 0.01 M solution of sodium bicarbonate be acidic, basic, or neutral?

5. When Zn plate is immersed in an HCl solution hydrogen gas bubbles can be seen. List all the mechanistic steps of the Zn + 2H+ reaction that account for this observation.

6. When 0.1 L of 0.1 M Mg(OH)2 solution is mixed with 0.1 L of 0.1 M of HNO3 solution, what is the the pH and the concentration of Mg2+ ions of the resulting mixture?

7. In a redox reaction, an increase of an oxidation state of one reactant must be accompanied by the same decrease of an oxidation state of another reactant. True or False? Explain your answer.

8. Reaction A + B ->P proceeds to completion. When you add 2 moles of A and 3 moles of B to an evacuated reaction chamber what is the result?

9. Consider the following gas phase reaction 2A -> P in which the product, P is formed when two A molecules collide. When the initial pressure of the gas A in the reaction chamber is increased from 0.5 atm to 1.5 atm what do you expect the initial rate of this reaction to be relative to the original set of conditions?

10. Consider again the gas phase reaction 2B <=> P in which the product, P is formed when two B molecules collide. Knowing the equilibrium constant of this reaction, K = 1.0, and that the initial pressure of B was 1 atm, what change in the pressure of the reaction chamber do you expect?

11. A 0.1 M solution of a weak acid has a pH of 2.4. Determine the value of the equilibrium constant Ka of this acid.

12. Consider the following three solutions of acetic acid (CH3COOH Ka=1.8 x 10-5) of different concentrations: 1) 0.500 M, 2) 0.100 M, and 3) 0.010 M. Which solution has the lowest (most acidic) pH, and which has the greatest percent dissociation? Show your work.

 

 

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