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August 27, 2014

Homework Help: Chemistry

Posted by Jack on Friday, September 23, 2011 at 12:27pm.

1. Molarity is to moles of solute over liters of solution as molality
is to
A. molar concentration over molal concentration.
B. moles of solute over kilograms of solvent.
C. molal concentration over molar concentration.
D. moles of solute over moles of solvent.


2. In describing an equilibrium reaction involving hydrogen gas, iodine gas, and hydrogen
iodide gas, all of the statements about equation Q = [HI]2  [H2] [I2] are true except for
which one?
A. Any solids are omitted from equilibrium expressions.
B. The brackets refer to “concentration of . . . ”
C. Coefficients from the original balanced equation (in this case, 2 HI) become exponents.
D. The products go to the denominator, and the reactants go to the numerator.


3. If the angle of collision between molecules A and B in a reaction is favorable, reaction
energy is less than when the angle of collision is unfavorable. If you look up the typical
activation energy for a given reaction in a table, the value you see will be for
A. minimum activation energy.
B. maximum activation energy.
C. average activation energy.
D. the range of values between minimum and maximum activation energy.


4. If a catalyst is used to alter the reaction rate of A + B → AB, we can expect a/an
A. increase in ΔH.
B. increase in the activation energy that initiates the reaction.
C. decrease in ΔH.
D. decrease in the activation energy that initiates the reaction.

5. Regarding solutions and solids, which statement is true?
A. If the solvent is water, the crystal lattice energy of a solid is absorbed.
B. Hydration energy is related to the attractions between solute particles.
C. If the solvent is water, the crystal lattice energy of a solid is released.
D. Hydration energy is related to the attractions between solvent particles.

6. Avogadro’s number gives us the number of
A. atoms in any element or compound.
B. particles in a mole of any element or compound.
C. atoms in an element.
D. particles in a sample.

7. A chemical formula containing the simplest whole-number ratio between elements in a
compound is called the _______ formula.
A. derivative C. composition ratio
B. composition D. empirical

8. Which one of the following statements is correct?
A. Solubility of solids and liquids is affected by randomness and temperature.
B. Increasing temperature and lowering pressure maximizes the solubility of a gas in a liquid.
C. Energy has no affect on solubility.
D. When a solid dissolves, the attractive forces are weakened, and entropy decreases.

9. For which of the following must the empirical formula be written with only one subscript?
A. C6H6 C. C2H6
B. C5H12 D. H2O2

10. Regarding electrolytes, all of the following statements are true except for which one?
A. Covalent bonds, such as those of sugar, make weak electrolytes in solution.
B. Ionic compounds often form strong electrolytes when in solution.
C. Ammonia is a weak electrolyte because it produces few mobile ions.
D. Mobile ions formed as a result of dissociation cause solutions to conduct electricity.

11. The equation for an equilibrium reaction is A + B AB. Following Le Chatelier’s
principle, if the concentration of “A” is increased, then
A. stress and equilibrium are not affected.
B. the equilibrium shifts to the left.
C. the eqilibrium shifts to the right.
D. a smaller concentration of products is formed.

12. If two immiscible liquids are joined in the same container, one liquid will rise to the top of
the container because of its
A. lower ionization energy.
B. lower density.
C. greater ionization energy.
D. greater density.

13. The volume in liters at STP for 15 grams of helium is
A. 3.75 L. C. 84 L.
B. 56.25 L. D. 89.6 L.

14. Picture two gases in an equilibrium solution in a sealed container such that the total volume
of the reactants, A + B, is equal to the total volume of the product, AB. If the volume
of the container is reduced from V to ˝V, we would observe
A. that the system remains at equilibrium.
B. an increase in the rate of forward reaction and an increase in AB.
C. a decrease in the rate of forward reaction and an increase in the concentration
of reactants.
D. that the equilibrium constant (KEQ) increases only slightly with respect to the ratio of product to reactants.

15. Picturing a sealed container of some solution, the temperature at which the vapor pressure
of a liquid equals the pressure of the gas acting on the liquid is the?
A. colligative standard.
B. freezing point for that solution.
C. boiling point for that solution.
D. freezing or boiling point for that solution.

16. Which statement best illustrates phase equilibrium?
A. Ice in a tray melts as the temperature goes up.
B. In a sealed container, water evaporates and condenses as the water level remains constant.
C. Ice in a tray evaporates directly from solid to water vapor in a process of sublimation.
D. In a sealed container, two gases interact such that reverse reactions precede forward reactions.

17. At 20° C, 100 grams of water can dissolve 72 grams of HCl. At this point, in terms of solubility, the solution is said to be?
A. supersaturated. C. saturated.
B. nearly saturated. D. balanced.

18. The equilibrium constant is the ratio of product concentration to reactant concentration at
equilibrium. A reaction will likely go to completion if the equilibrium constant
A. is very high. C. is very low.
B. is moderate. D. increases with rate of reaction.

19. In the compound KClO3, what is the percent composition to the nearest whole number of potassium?
A. 29% C. 35%
B. 32% D. 39%

20. In a lab experiment, we compare the rates of reactions between oxygen and a substance,
S, that oxidizes at room temperature. In Experiment 1, we expose 5 grams of S to the air.
In Experiment 2, we expose 5 grams of S to the air, but this time, S is ground into a powder.
What can we expect to observe, and why?
A. There will be no change in the reaction rates.
B. The reaction rate for Experiment 2 will be much slower due to increased surface area.
C. The reaction rate for Experiment 2 will be much faster due to increased surface area.
D. The reaction rate for Experiment 1 will be much faster due to concentration of reactants.

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