1) Octane (C8H18) oxidizes at high temperatures in the presence of oxygen to form CO2 and H2O. How many moles of CO2 are produced per mole of octane?
2) Methane (CH4) also burns in the presences of oxygen to form CO2 and H2O. How many lbs of CO2 are formed when 1 lb of methane is burned?
3) Hypochlorous acid (HOCl) is also referred to as "chlorine" as is used as a disinfectant for swimming pools and drinking water. This is a weak acid with a pKa = 7.53. Which of the following represents the correct equilibrium equation for this weak acid?
4) For an endothermic reaction, an increase in temperature causes an increase in the equilibrium constant, K. In this case an increase in temperature would cause:
An increase in the concentration of products over reactants
No change in concentrations other either reactants or products
An increase in reactants over products
5) At a pH = 7, which of the following is true?
The concentration of carbonate is higher than the concentration of bicarboante
The concentration of bicarbonate is higher than the concentration of carbonate
The concentration of carbonate and bicarbonate are the same
6. The equilibrium constant of a weak acid is 10-5. What is the pKa?
0.000001
10-5
5
-5
7) Which of the following can be used to increase the pH of water?
Calcium carbonate
CO2
Hydrochloric acid
Acetic acid
8) Chlorine bleach (hypochlorous acid) is more effective at:
High pH (> 8)
Neutral pH (6 - 8)
9) A strong acid:
Partially dissociates (part of the reactant left)
Dissociates completely (no reactant left)
Does not dissociate at all (all the reactant is left)
10) You can oxidize organic waste (C70H110O50N) using oxygen according to the following equation:
C70H110O50N + O2 = CO2 + H2O + NH3
If you decompose 100 lbs of waste, how many lbs of CO2 will you create? (175 lb CO2)
11) The following organic waste can be consumed by bacteria in the presence of oxygen.
C75H110O62N + O2 = CO2 + H2O + NH3
a. Balance the chemical equation above. (show your work)
___C75H110O62N + ___O2 = ___CO2 + ___ H2O + ___ NH3
b. Water contains 100 mg/L of organic waste (C75H110O62N). What is the concentration of oxygen dissolved in the water required to decompose all the organic waste?
NH3 (ammonia - more toxic) can also become NH4+ (ammonium - less toxic) according to:
NH4+ = H+ + NH3 pKa = 9.21
c. Calculate the ratio of NH3 to NH4+ at a pH of 6.5.
d. If the pH is raised to 8, would the water be more or less toxic in terms of ammonia? Explain your answer.
12) After treating the water you need to decrease the pH back to 6.5. The water is held in a 200,000 gallon "pond".
a. You have a 3 M HCl solution. How many mLs of this solution are required to change the pH from 9.5 to 6.5?
b. Another option for lowering the pH is to add citric acid (C6H8O7). Citric acid has a pKa = 3.1. How many grams of citric acid do you need to add to a 200,000 gallon pond to lower the pH from 9.5 to 6.5?