NSCI 100 NSCI100 Quiz 4 with Answers (UMUC)

NSCI 100 NSCI100 Quiz 4

1. A friend argues that if mass were really conserved he would never need to refill his gas tank. What explanation do you offer your friend?
2. What is a chemical reaction?
3. What is a chemical equation?
4. Given the following generic chemical reaction, which is the product? - X → Y
5. For the following balanced reaction, which of the following is a solid? - 2 Na(l) + Cl2(g) → 2 NaCl(s)
6. For the following balanced reaction, which of the following is a gas? - 2 Na(l) + Cl2(g) → 2 NaCl(s)
7. Why is it important for a chemist to know the relative masses of atoms?
8. How does formula mass differ from atomic mass?
9. The relative mass of carbon is 3/8 that of an oxygen molecule. How many grams of carbon are needed to have the same number of particles as found in 32 grams of oxygen molecules?
10. Which has the greatest number of molecules?
11. How many grams of gallium are there in a 145 gram sample of gallium arenside, GaAs?
12. What is a reaction rate?
13. Why might increasing the temperature alter the rate of a chemical reaction?
14. What is the activation energy?
15. The yeast in bread dough feeds on sugar to produce carbon dioxide. Why does the dough rise faster in a warmer area?
16. Why does a glowing splint of wood burn only slowly in air, but rapidly in a burst of flames when placed in pure oxygen?
17. Why is heat often added to chemical reactions performed in the laboratory?
18. Is the synthesis of ozone, O3, from oxygen, O2, an example of an exothermic or endothermic reaction?
19. Which of the following statements about catalysts is NOT true?
20. Which of the following statements accurately describes the action of ozone?
21. What is the environmentally unfriendly component of chlorinated fluorocarbons that ultimately damages ozone?
22. What is the main difficulty in trying to eliminate chlorinated fluorocarbons from the atmosphere?
23. The chlorinated fluorocarbons molecules are acting as a(n) ________ by converting hundreds of thousands of molecules before they are inactivated.
24. How is ozone produced in the upper atmosphere?
25. A catalytic converter increases the amount of carbon dioxide emitted by an automobile. Is this good news or bad news?
26. What is an exothermic reaction?
27. What is an endothermic reaction?
28. If it takes energy to break bonds and you gain energy in the formation of bonds, how can some reactions be exothermic while others are endothermic?
29. How many bonds between nitrogen and hydrogen are formed if you react nitrogen with hydrogen according to the following reaction? - N2 + 3H2 → 2 NH3
30. Given that the bond energy of N2 is 946 kJ/mole, the bond energy of O2 is 498 kJ/mole and the NO bond energy is 631 kJ/mole, how much energy is required to react 1 mole of nitrogen molecules according to the following reaction? - N2 + O2 → 2 NO
31. Which of the following reaction energies is the least exothermic (but still an exothermic reaction)?
32. Which of the following reaction energies is the most endothermic?
33. Which is higher in an endothermic reaction: the potential energy of the reactants or the potential energy of the products?
34. Bond energies increase in going from C-N (lowest) to C-O to C-F (highest). Explain this trend based upon the atomic sizes of these atoms as deduced from their positions in the periodic table.
35. Wild plants readily grow all by themselves yet the molecules of the growing plant have less entropy than the materials used to make the plant. How is it possible for a there to be this decrease in entropy for a process that occurs all by itself?