1)Hydrogen peroxide solutions are commercially available and have a range of uses. The active ingredient, hydrogen peroxide, H₂O₂, undergoes decomposition in the presence of a suitable catalyst according to the reaction 2H₂O₂(l) → 2H₂O(l) + O₂(g)
In this reaction, oxygen
A. only undergoes oxidation.
B. only undergoes reduction.
C. undergoes both oxidation and reduction.
D. undergoes neither oxidation nor reduction.

Solution

2) Dilute nitric acid reacts with anhydrous sodium carbonate to produce carbon dioxide gas.

In an experiment, 0.142 mol anhydrous Na₂CO₃ powder was added to excess HNO₃ in solution, in a 2.00 L reinforced, sealed, metal vessel. Pressure and temperature sensors were used to monitor the reaction. The vessel was initially at 101.3 kPa and 22.0 °C. When the reaction was complete, the final temperature was 24.1 °C. What is the additional pressure, in kPa, inside the vessel due to the carbon dioxide gas after the completion of the reaction? (Assume that the volume of the solution in the vessel is negligible.)
A. 349
B. 175
C. 28.3
D. 14.2

Solution

The predicted results were not observed. The class was asked to suggest some hypotheses to explain the unexpected result. Which one of the following hypotheses could not explain the unexpected result?
A. The reaction rate might have been too slow for the time allowed.
B. An equilibrium was established and [Cu²⁺] was too low to be visible.
C. A bromine solution was accidentally used in place of the iodine solution.
D. The surface of the copper metal was greasy.

Solution

4) Standard solutions of sodium hydroxide, NaOH, must be kept in airtight containers. This is because NaOH is a strong base and absorbs acidic oxides, such as carbon dioxide, CO₂, from the air and reacts with them. As a result, the concentration of NaOH is changed to an unknown extent.

a. CO₂ in the air reacts with water to form carbonic acid, H₂CO₃. This can react with NaOH to form sodium carbonate, Na₂CO₃.
i. Write a balanced overall equation for the reaction between CO₂ gas and water to form H₂CO₃.

Soluiton
ii. Write a balanced equation for the complete reaction between H₂CO₃ and NaOH to form Na₂CO₃.

Solution

b. A 10.00 L container is completely filled with a freshly made 0.1000 M NaOH solution. During a Chemistry class, 9.90 L of the solution is used and air enters the empty space above the remaining solution before the container is completely sealed off from the outside air. The container is then opened. Air enters the container at 101.3 kPa and 21.5 °C. Assume that the concentration of CO₂ in the air is 0.0400 %(v/v).

Solution

c) Calculate the amount of NaOH, in mol, that would be present in the solution that remains in the container. Assume that the NaOH did not react with the CO₂ in the air that entered when the container was opened.

Solution

d) The container is then shaken thoroughly, ensuring that all the CO₂ in the air is absorbed into the solution. Calculate the resulting concentration of NaOH in the solution in the container.

Solution