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Q 4 & 6 p189

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

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Q 4 & 6 p189

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  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. 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. 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)

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

  7. 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

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