Download std 8 9 reviewanswers

Name: ______________________
Date: ___________ Period: _____
8. Chemical reaction rates depend on factors that influence the frequency of collision of reactant molecules. As
a basis for understanding this concept:
a. Students know the rate of a reaction is the decrease in the concentration of reactants or the increase in the
concentration of products with time.
1. Which of these describes the rate of this chemical reaction?
Cl2 + H2 ↔ 2HCl
A an increase in HCl and H2with time
C an increase in HCl with time
B an increase in H2 and Cl2 with time
D a decrease in HCl and Cl2 with time
CO2 + H2O ↔ C6H12O6 + O2
2. Which of these describes the rate of this chemical reaction?
A an increase in C6H12O6 and O2with time
C an increase in CO2 and H2O with time
B an increase in C6H12O6 with time
D a decrease in CO2 and H2O with time
3. The rate of the following reaction can be described as: Fe + 2HCl ↔ FeCl2 + H 2
A appearance of FeCl2
B decrease in the amount of H2
C appearance of Fe
D absence of O2
4. The rate of the reaction is measured by calculating change in:
A. Increase of concentration in products over time B Decrease of concentration in products over time
B. Increase of concentration in reactants over time D Decrease of concentration in products & reactants over time
b. Students know how reaction rates depend on such factors as concentration, temperature and pressure.
5. Which of the following changes will cause an increase in the rate of the reaction below?
catalyst
C H  Br  C H Br  HBr
6 6
2
6 5
A
C
increasing the concentration of Br2
increasing the concentration of HBr
B decreasing the concentration of C6H6
D decreasing the temperature
6. If the reaction takes place inside a sealed reaction container, then which of these procedures will cause a
decrease in the forward rate of reaction?
2CO + O2 ↔ 2 CO2
A raising the temperature of the reaction chamber
B removing CO2 as it is formed
C increasing the concentration of CO2
D adding more CO to the reaction chamber
7. A change in temperature affects the reaction rate because as the temperature increases:
A
C
more collisions with the required energy occur
pressure decreases
B The number of molecules increases
D molecules expand and take up more room
Zn(s) + 2HCl(aq)  ZnCl2(aq) + H2(g)
The reaction occurs more slowly when a single piece of zinc is used than when the same mass of
powdered zinc is used. Why does this occur?
A the powdered zinc is more concentrated
B the powdered zinc required less activation energy
B the powdered zinc generates more heat energy
D the powdered zinc has a greater surface area
8. Given the reaction:
c. Students know the role a catalyst plays in increasing the reaction rate.
9. A catalyst can speed up the rate of a given chemical reaction by
A increasing the equilibrium constant in favor of products.
B lowering the activation energy required for the reaction to occur.
C raising the temperature at which the reaction occurs.
D increasing the pressure of reactants, thus favoring products.
10. H2O2, hydrogen perioxide, naturally breaks down into H2O and O2 over time. MnO2 manganese dioxide,
can be used to lower the energy of activation needed for this reaction to take place and, thus, increase
the rate of reaction. What type of substance is MnO2?
A a catalyst
B an enhancer
C an inhibitor
D a reactant
11. Which reaction diagram shows the effect of using the appropriate catalyst in a chemical reaction?D
*d. Students know the definition and role of activation energy in a chemical reaction.
12. Which of the following is used to stabilize the transition state?
A energy absorbed by the reaction B nuclear energy
C energy released by reaction
D activation energy
13. Which of the following statements is false?
A The larger the amount of activation energy, the more unstable the transition state is
B The activation energy is the difference energy between the products and the transition state
C A catalyst works by lowering the activation energy for the reaction
9. Chemical equilibrium is a dynamic process at the molecular level. As a basis for understanding this concept:
a. Students know how to use Le Chatelier’s principle to predict the effect of changes in concentration,
temperature, and pressure.
14. When a reaction is at equilibrium and more reactant is added, which of the following changes is the
immediate result?
A the reverse reaction stays the same
B the forward reaction rate increases
C the reverse rate decreases
D the forward reaction rate remains the same
15. In which of the following reactions involving gases would the forward reaction be favored by an increase
in pressure?
A A + B ↔AB
BA+B↔C+D
C 2A + B↔ C + 2D
D AC ↔ A + C
16. Which action will drive the reaction to the right? 4HCl + O2 ↔ 2H2O + 2Cl2 + 113 kJ
A heating the equilibrium mixture
C decreasing the oxygen concentration
B adding water to the system
D increasing the system’s pressure
17. The reaction shown below occurs inside a closed flask. What action will shift the reaction to the left?
NO2 + CO ↔ NO + CO2
B raising the total pressure in the flask
D venting some CO2 gas from the flask
A pumping CO gas into the flask
C increasing NO concentration in flask
18. What kind of change will shift the reaction to the right to form more products?
A a decrease in total pressure
C increase in the pressure of NH3
NH4Cl + heat ↔ NH3 + HCl
B increase in HCl concentration
D decrease in the temperature
b. Students know equilibrium is established when forward and reverse reaction rates are equal.
19. In a sealed bottle that is half full of water, equilibrium will be attained when water molecules
A cease to evaporate
B begin to condense
C are equal in number for both the liquid and gas phase D evaporate and condense at equal rates
20. At equilibrium, the forward reaction rate is:
A greater than the reverse reaction rate
C equal to the reverse reaction rate
B less than the reverse reaction rate
D independent of the reverse reaction rate