Chem 1405 Fall 2012
Test 3 Total Score 35
Answer all questions:
1. Why is equilibrium described as dynamic?
A.because processes are still taking place
B.because an equilibrium mixture is typically a solution and therefore fluid
C.because the rates of the opposing processes can change at any time when at equilibrium
D.because there is an exchange of heat at equilibrium
2. Which of the following statements is NOT true?
A.Vapor pressure increases when the attractive forces between molecules increases.
B.Boiling point decreases when the attractive forces between molecules decreases.
C.The surface tension of water is reduced in the presence of dissolved solutes.
D.Melting point increases when the attractive forces between molecules increases.
3. What happens to the concentration of NaCl when 500-mL of water is added to a
NaCl?
A. The concentration increases.
B.The concentration decreases.
C.The concentration does not change.
D.The NaCl solidifies.
1mM solution of
4. The Tyndall effect can be used to identify what type of solution?
A. a solution of macromolecules
B.a colloidal solution
C.a heterogeneous solution
D.a light-sensitive solution
5. In order to determine the number of moles NaCl contained in 2-L of 0.5 M NaCl solution, one must
A.multiply the volume by the molarity
B.divide the volume by the molarity
C.divide the molarity by the volume
D.multiply the volume by both the molarity and Avogadro’s number
6. What must be present in order to cause osmotic pressure?
A. a mechanical force
B.a semi-permeable membrane
C.two solutes in the same solution
D.a U-tube
7. The amount of energy required for a reactive collision to occur between two reactants is referred to as
A.the heat energy of reaction.
B.the activation energy
C.the kinetic energy
D.the transition state energy
6. What can be said about the reactants and products of a reaction that has reached a state of dynamic
equilibrium?
A. the concentration of reactants is less than the concentration of products
B. the rate of reaction for the formation of products is equal to the rate of reaction for the decomposition of
products
C. the reaction has switched directions
D. none of the above
7. Which of the following statements about water is TRUE?
A. Water can ionize.
B. Water can function as both an acid and a base.
C. The concentration of hydronium ion and hydroxide ion in pure water is constant
D. All of the above
8. If the concentration of hydronium ions is greater than the concentration of hydroxide ions in an aqueous
solution, what must be true of the ion-product of water?
A. It is lower than 1  10-14.
B. It is greater than 1  10-14.
C. It remains 1  10-14.
D. It becomes 0.
9. If the pH of a solution is 9, what is the concentration of hydronium ions?
A. There are no hydronium ions since the solution is basic.
B. The amount of hydronium ions is less than the amount of hydroxide ions.
C. The amount of hydronium ions is equal to 1  10-14 M.
D. The concentration of hydronium ions is equal to 1  109 M.
10. What will be the result if an acid is added to a buffer?
A. The pH of the buffer will decrease.
B. The acid will react with the conjugate base of the
C. The pH of the buffer will stay the same.
D. Both b and c will occur.
buffer.
11. When an acid-base titration reaches the equivalence point, which of the following
true?
A. The volume of acid mixed with base is equal.
B. The moles of acid are equal to the moles of base.
C. The endpoint of the titration has been reached.
D. The reaction has gone to completion.
statements are NOT
12. The boiling point of a liquid ___________________ with decreasing atmospheric pressure.
13. Reactions that absorb heat are called _________________ reactions.
14. An amorphous solid lacks _____________________________________________.
2
15. As a solid is heated, its temperature increases from 10ºC to 25ºC, remains at 25ºC for 5 minutes, and then
increases to beyond 45ºC. What is the most reasonable conclusion that can be drawn about this substance? 1
A. Its boiling point is 25ºC.
B. Its melting point is 25ºC.
C. Its boiling point is 45ºC.
D. Its melting point is 45 ºC.
16. Arrange these molecules in order of increasing boiling points:
I. CH3CH2OH
III. CH3OCH3
2
II. H2O
IV. CH3CH2CH3
17. What kind of interactions account for the extreme stability of diamonds?
A. Hydrogen bonding
B. Covalent bonding
C. London forces
D. Ionic bonding.
18. A solution prepared by dissolving 4.35 g of a powdered nonelectrolyte in 375 mL of water has an osmotic
pressure of 1.41 atm at 28.3ºC. What is the molar mass of the nonelectrolyte?
2
A. 19.1 g/mol
B. 203 g/mol
C. 301 g/mol
D. 821 g/mol
19. A solution contains 50.0 g of water and 1.20 g of solute. Calculate the % w/w concentration.
2
20. What is the molarity of a solution made by dissolving 32.0 g of KCl in enough water to make 425 mL of
solution?
2
21. When 20.0 mL of a 0.500 M salt solution is diluted to 1.00 L, the concentration of the diluted solution is:
22. How many moles of Na2SO4 must be added to 0.500 L of water to produce a 2 M solution of Na+ ions?
2
2
23. Consider the reaction CH2 =CH2 + H2 + Pt  CH3CH3 + Pt
4
A. Write an equilibrium constant for this reaction
B. What is the catalyst in the reaction?
C. What would happen to the system if 10moles of H2 is introduced into the system?
D. What would happen if the concentration of Pt is altered?
24. Given the reaction H2(g) + I2(g)
2HI(g), when 2.00 mol of each reactant are mixed in a 1.00-L vessel
at a certain temperature and equilibrium is reached, 3.50 mol of HI is produced. The equilibrium constant for
this:
3
A. 14.1
B. 49.2
C. 56.7
D. 196
25. What will happen when this equilibrium system is heated?
H2(g) + Br2(g)
2HBr(g) + heat
2