Chem 106

Final Exam

NAME____________________Date__________________________

 

 

1.All of the following half-reactions are balanced EXCEPT

  1. 2H2O + 2e -→ H2 + 2OH-
  2. NO 3- + 4H+ + 3e-→ NO + 2H2O
  3. 2Ta + 5H2O → Ta2O5 + 10H+ + 10e-
  4. H3PO3 + H2O → H3PO4 + 2H+ + 2e-

e.       Fe3+ → Fe2+ + e-

 

2 &3. For the following oxidation-reduction reaction :

8H+(aq) + 6Cl-(aq) + Sn(s) + 4NO3-(aq) --> SnCl62-(aq) + 4NO2(g) + 4H2O

Indicate on the line below the oxidizing agent and write the half-reaction indicating oxidation numbers.

2)________________________________________

Indicate on the line below the reducing agent and write the half-reaction indicating oxidation numbers.

3)________________________________________

4.      Balance the following REDOX reaction in aqueous acid.

Zn + SO4 2- → Zn 2+ + SO2

 

 

 

 

5.      In the electrolysis of water, what product is found at the anode? In a weak sodium chloride solution, what products would you find at the anode?


6.      Consider the half-reactions under standard conditions:

Zn 2+ + 2e - → Zn (s) E0= -0.763 V

Cu2+ + 2e - → Cu (s) E0= + 0.337 V

What is the net voltage expected for an electrochemical cell with these half reactions?___________________________

7.      In the spontaneous reaction represented as follows:

Zn (s) + Cu2+ → Zn 2+ + Cu (s)

What is the oxidizing agent?_____________________________

8.      Under what set of conditions will real gases deviate from Ideal Gas behavior?

a.       High temperature and low pressure

b.      Low temperature and high pressure

c.       High temperature and high pressure

d.      Low temperature and low pressure.

 

9. Which of the following plots, A through D, is representative of the behavior of a quantity gas at constant temperature?

A B C D

 

10.              Which of the following indicate strong intermolecular forces within a liquid? Check all that apply :

  1. A high boiling point._____
  2. A high vapor pressure._____
  3. A high heat of vaporization.____
  4. A high freezing point._____

 


11.  A sample of nitrogen gas has a pressure of 698 mm Hg in a 5.00 L flask. What is the pressure of the gas if it is compressed into a 0.125 L flask? Temperature is constant.

 

 

 

 

 

 

 

12.  A gas sample is contained in a 250 ml flask. The pressure is 750mm Hg and temperature is 37 Celcius. The gas is cooled to 15.0 celsius and now occupies 120 ml volume. What is the new pressure?

 

 

 

 

 

 

13.  A 1.4 g sample of carbon monoxide gas is contained in a 250 ml flask at 27 o C. Find the pressure in the flask.

 

 

 

 

 

 

14.  For the reaction 4A +3B 2C + D , write out the expression for the equilibrium constant. How would it be expressed in terms of partial pressure?

 

 

 

 

 

 

 

15.  The pOH of a particular solution is 1.625. What is the pH ? What is the hydronium ion and hydroxyl ion concentration? What must the product of the two equal?


16.  You are in a lab at STP. You dissolve 114.10 g of sucrose, C12H22O11 in 300 g of water. What are the molarity, percent mass, mole fraction and molality of sucrose? Determine the theoretical freezing point and boiling point of the solution.. The freezing point depression constant for water is -1.853 oC/ m and the boiling point elevation constant is 0.512 oC/ m. What is the Vant Hoff factor of the solution and why?


17.              Fill in the table

pH

[H3O +]

[OH-]

Acidic or Basic?

1.47

 

 

 

 

3.5 x 10 -7

 

 

 

 

1.0 x 10 -7

 

9.60

 

 

 

 

 

 

 

 

 

 

 

 

 

N2 + H2 NH3 Is the equation balanced?

Find the reaction quotient and determine whether the reaction progress is forward or backward. The equilibrium constant is 61.1 at 500K. At the time of measurement the partial pressures of each are:

N2 =.15 atm., H2 =.17 atm., NH3 =1.41 atm.

 


  1. Dinitrogen pentoxide decomposes to nitrous oxide and oxygen at high temperature as follows:

2 N2O5 4 NO2 + O2

The rate constant for the decomposition of N2O5 is as follows: K =0.00053 M/s. What is the Half life? What will the concentration of N2O5 be after 6 hours?


20.        Phosphorus penta-chloride PCl5 reversibly decomposes into Phosphorus tri-chloride and chlorine gas:

PCl5 PCL3 + CL2

The equilibrium constant is Kc =1.8 at 300K. If the initial concentration of PCl5 is 0.46 M, what will be the concentration of products after time elapses and the reaction comes to equilibrium?