General Chemistry: Chapter 7 Test
1. In endothermic reactions:
a. energy is releasedc. heat is given off
b. products have less energy than reactantsd. products have more energy than reactants
2. Because it takes less energy to get them started, most chemical reactions are exothermic.
a. Trueb. False
3. What happens to atoms in all chemical reactions?
a. They are destroyed and re-created.c. They are rearranged.
b. They are transformed into different atoms.d. They change their state of matter.
4. The input of energy that is required to start a chemical reaction is called the:
a. achievement energyc. acquisition energy
b. active energyd. activation energy
5. When balancing a chemical equation, you are allowed to:
a. change coefficientsc. add new reactants
b. change subscriptsd. add new products
6. In a chemical reaction, the energy contained in the reactants is _____ the energy contained in the products.
a. equal toc. greater than
b. less thand. not the same as
7. In order to react, chemical substances must:
a. collidec. be gases
b. be at a very high temperatured. be mixed by a licensed professional
8. Making a pizza would be most like a _____ reaction.
a. decompositionc. single displacement
b. synthesisd. double displacement
QUESTIONS 8-12 DEAL WITH THE REACTION BELOW. EACH COMPOUND CORRESPONDS WITH A LETTER ON YOUR ANSWER KEY. MARK ALL ANSWERS THAT APPLY.
Given the balanced chemical equation:C6H12O6 (aq) + 6 O2 (g) 6 CO2 (g) + 6 H2O (l)
A B C D
9. Which compound(s) is/are gases?
10. Which compound(s) is/are dissolved in water?
11. Which compound(s) is/are products?
12. Which compound(s) is/are liquids?
QUESTIONS 13-16 DEAL WITH THE REACTION BELOW.
Given the balanced chemical equation:Ca(OH)2 + 2 HCl CaCl2 + 2 H2O
A. 1B. 2C. 4D. 6E. 8
13. If 1 mole of Ca(OH)2 reacts with excess HCl, how many moles of CaCl2 are formed?
14. If 2 moles of HCl react with excess Ca(OH)2, how many moles of CaCl2 are formed?
15. If 4 moles of Ca(OH)2 react with excess HCl, how many moles of H2O are formed?
16. If 4 moles of HCl react with excess Ca(OH)2, how many moles of H2O are formed?
17. The chemical formula of sulfuric acid is H2SO4. A chemical formula tells us:
a. the elements in the substancec. both a and b
b. the number of atoms of each type in 1 moleculed. neither a nor b
QUESTIONS 18-19 DEAL WITH THE FOLLOWING CHEMICAL EQUATION.
2 C2H2 + 5 O2 4 CO2 + 2 H2O + energy
When acetylene gas reacts with oxygen, energy is released in the form of heat and light.
18. Where is chemical energy stored in compounds?
a. in the nucleus of the atomc. in the bonds between atoms
b. in the electrons of each atomd. in the bonds within each atom
19. Which compounds have more energy?
a. reactantsb. products
20. The effect of a catalyst is to _____, and this is caused by the _____.
a. lower the activation energy…higher rate of the reaction
b. increase the rate of the reaction…higher activation energy
c. decrease the rate of the reaction…lower activation energy
d. increase the rate of the reaction…lower activation energy
21. In a chemical equation, if a reactant or product is followed by (aq), it means that the:
a. substance is in adequate supplyc. reaction is a quick one
b. substance is dissolved in waterd. equation for the reaction is balanced
22. In a balanced chemical equation, the coefficients are important because they:
a. define the chemical properties of the substances
b. tell whether the reaction is exothermic or endothermic
c. give the ratios for all of the chemicals in the reaction
d. tell what type of chemical reaction (synthesis, single displacement, etc.) the reaction is
23. The combustion of gasoline in an automobile engine is an example of:
a. an exothermic reactionc. equilibrium
b. an endothermic reactiond. a physical change
24. In the reaction H2 + I2 2 HI, what is the ratio of the hydrogen gas molecules to the molecules of HI formed?
a. 1:1b. 2:1c. 1:2d. not enough information
25. In a chemical reaction, the mass of the products is _____ the mass of the reactants.
a. greater thanc. equal to
b. less thand. greater or less than
IN QUESTIONS 26-33, CLASSIFY THE FOLLOWING REACTIONS.
26. CO2 C + O2A = combustion
27. NaI + Cs CsI + NaB = synthesis
28. NaCl + AgNO3 NaNO3 + AgClC = decomposition
29. S + Cl2 SCl2D = single displacement
30. Pb(NO3)2 + Mg Pb + Mg(NO3)2E = double displacement
31. 2 O2 + N2 N2O4
32. Li3PO4 3 Li + P + 2 O2
33. Mg + 2 HCl MgCl2 + H2
ON YOUR ANSWER KEY, BALANCE THE FOLLOWING CHEMICAL EQUATIONS (Q’S 34-37). YOU NEED NOT WRITE THE CHEMICALS; JUST WRITE THE SUBSCRIPTS IN ORDER.
34. CoCl2 + Fe FeCl3 + Co
35. NaNO3 NaNO2 + O2
36. H2 + O2 H2O
37. Fe + H2O Fe3O4 + H2
ANSWER Q'S 38-41 ON YOUR ANSWER KEY.
38. Write a balanced chemical equation for the combustion of methane (CH4) to form carbon dioxide and water. You may leave off the reaction conditions.
39. Answer following questions on your answer key.
a. A solid sample of silver nitrate (AgNO3) is mixed with water. If the nitrate ion (NO31-) has a 1- charge, what ions are present in the solution?
b. A solid sample of sodium bromide (CaCl2) is mixed with water. What ions are present in this solution?
c. The two solutions are mixed. What four ions are present in the resulting solution?
d. Looking at the solubility chart below, list any pair(s) of ions that form a solid precipitate.
e. Looking at the solubility chart below, list any pair(s) of ions that remain in solution.
f. Write an overall reaction for the above situation.
g. Write a net ionic reaction for the above situation.
40. The Statue of Liberty consists of a steel framework that is covered with a thin "skin" of copper. When copper is exposed to air, it combines with oxygen to form copper oxide, CuO. CuO has the light green color that we see on the Statue. With the right chemicals, though, the CuO can be removed and the bare, "copper-colored" copper is again visible.
Why is the bare copper underneath NOT green?
41. We discussed the effect of a catalyst on an exothermic reaction in class. A catalysts has the same effect on an endothermic reaction.
- Draw a graph showing an endothermic reaction without a catalyst.
- Draw a second graph of the same reaction, but this time with a catalyst added.
- State 2 effects that a catalyst has on a reaction.
- State what does not change about a reaction, whether a catalyst is added or not.