1. Q 4 & 6 p189
Q: Why do all reactions need added energy to get started?

2. Q 4 & 6 p189 Q: Why do all reactions need energy to get started?
A: Because at least one chemical bond has to be broken before the reaction can proceed (1 pt)

3. Q 4 & 6 p189
6. Calcium oxide, CaO, is used in cement mixes. When water is added, heat is released as CaO forms calcium hydroxide, Ca(OH)2. What signs are there that this is a chemical reaction? Which has more chemical energy, the reactants or products? Explain your answer.

4. Q 4 & 6 p189
6. Calcium oxide, CaO, is used in cement mixes. When water is added, heat is released as CaO forms calcium hydroxide, Ca(OH)2. What signs are there that this is a chemical reaction? Which has more chemical energy, the reactants or products? Explain your answer.
ANSWERS:
Signs: Heat and new substance. (1 pt)
Energy: Reactants have more chemical energy since some chemical energy is converted and released as heat during reaction. (1 pt)

5. Q 4 & 6 p189
6. Calcium oxide, CaO, is used in cement mixes. When water is added, heat is released as CaO forms calcium hydroxide, Ca(OH)2. What signs are there that this is a chemical reaction? Which has more chemical energy, the reactants or products? Explain your answer.
BTW: CaO has also been used in self-heating hot beverage cans. But, they sometimes blew up or melted, and are no longer on the market.
ANSWERS:
Signs: Heat and new substance. (1 pt)
Energy: Reactants have more chemical energy since some chemical energy is converted and released as heat during reaction. (1 pt)

6. Q 4 & 6 p189 Which of the following are exothermic or endothermic?
Paper burning
Plastic becoming brittle in sun
Firecracker exploding

7. TOTAL POSSIBLE SCORE = 6 PTS
Q 4 & 6 p189
Which of the following are exothermic or endothermic?
Paper burning
Plastic becoming brittle in sun
Firecracker exploding
EXO (1 pt)
ENDO (?)
EXO (1 pt)
TOTAL POSSIBLE SCORE = 6 PTS

8. 310: 20 g CaO CaO + H2O > Ca(OH)2 • 1 mole CaO = (40 + 16) g = 56 g
• 20 g CaO = 20 / 56 = 0.36 mole
• 1 mole H2O = 18 g
• 0.36 mole H2O = 0.36 • 18 = 6.5 g = 6.5 ml