Chemistry 114
Fourth Hour Exam
Name:____________
(2 points)
Please show all work for partial credit
1.
A. (3 points) What is the pH of .0062M HBr?
B. (3 points) If an HNO3 solution has a pH of 6.2, what is the concentration of NO 3in the solution?
C. (3 points) What is the pH of .0062M sodium hydroxide?
D. (3 points) If a calcium hydroxide solution has a pH of 10.5, what is the
concentration of the calcium ion in this solution?
2. If a solution of weak base is .01% ionized when the base has a concentration of .025M
A. (6 points) What is the pH of the solution?
B.(6 points) What is the KB of the base?
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3. (14 points) Are the following compounds acids, bases, or neutrals?
A. HCOOH ___________
B. HCOONa ____________
C. Lithium bromide _____________
D. CH3NH2 ____________
E. CH3NH3Cl ____________
F. Nitrogen dioxide ____________
G. Rubidium oxide ____________
4. Below is the titration curve of a weak acid with a strong base.
A. (2 points) Where is the Stoichiometric (Equivalence) point on this curve?
B. (2 points) What is the pKa of this acid?
C. (2 points) What equation would you use to calculate the pH of the solution at the
very beginning of the curve (Where no base has been added)?
D. (2 points) What equation would you use to calculate the pH at the stoiciometric
(equivalence) point?
E. (2 points) If you had to do this titration with an indicator, which indicator would you
choose;
Methyl red (pKa=5.0), Cresol red (pKa=8.46) or alizarin yellow (pKa=11.2)?
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5. Use the data in the following table to answer these questions:
Compound
S (J/K)
C3H8(g)
270.3
CO2(g)
213.8
H2O(g)
188.8
O2(g)
205.2
A. (3 points) Write the equation for the combustion of C3H8.(react with O2 to yield
CO2 and H2O)
B. (3 points) Balance the above equation.
C. (6 points) Calculate ÄS.
6. If the reaction A6B
If ÄH= +10kJ/mol ÄS=+ 35J/KAmol
a.) The reaction is Favorable at all T
b.) Favorable only at high T
c.) Favorable only at low T
d.) Never favorable
(Circle one)
If ÄH= -10kJ/mol ÄS=- 35J/KAmol
a.) The reaction is Favorable at all T
b.) Favorable only at high T
c.) Favorable only at low T
d.) Never favorable
(Circle one)
If ÄH= -10kJ/mol ÄS=+ 35J/KAmol
a.) The reaction is Favorable at all T
b.) Favorable only at high T
c.) Favorable only at low T
d.) Never favorable
(Circle one)
If ÄH= +10kJ/mol ÄS=- 35J/KAmol
a.) The reaction is Favorable at all T
b.) Favorable only at high T
c.) Favorable only at low T
d.) Never favorable
(Circle one)
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7. (2 points each answer)
Give the numerical value of Qco ______________
Given that KC for the reaction HAWH+ + A- is 1.8x10-5M , what is the thermodynamic
equilibrium constant (K) for this reaction? ______________.
What are the units for this K? _____________.
What is the third law of thermodynamics?
What is meant by an entropy favored reaction?
What is thermal disorder?
8. A. (4 points) If a reaction has a ÄGo of + 10 kJ/mol at 200K
What is the K for this reaction 200K
B.(4 points) If the same reaction has a K of 50 at 300K
What is the ÄG of this reaction at 300K?
C. (4 points) What is the ÄH for this reaction?
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