Reference no: EM131084158

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?