angela asked in 科學化學 · 1 decade ago

理化 題目的答案是不是算錯阿?(英文)

各位大大~ 這幾題的答案是不是有給錯? 如果有請給我正確答案 如果沒錯,請解給我看好嗎? 感謝

(題目都是有關energy的)

1. Some hot tea has cooled from 95℃ to 23℃. Calculate the energy released in joules(J) if the sample of tea has a mass of 50.0g . Assume that the tea has the same specific heat(比熱) as water, 1.00 cal/g℃.

Ans: 15000 J

2. What is the heat energy in joules released when 15.0 g of gold cools from 215℃to 35℃ ? Ans:350 J

3. An ice cube tray is filled with 125 g of water and placed in a freezer. How many joules of heat are removed by the freezer compartment to form ice cubes at 0℃. Ans:42000 J

4. When 0.02 oz of a milk-chocolate candy bar undergoes combustion in a calorimeter, the temperature of 500.0 g of water rises from 18℃ to 76℃. How many kilocalories are available in 1.00 oz of milk chocolate ? Ans:150kcal

1 Answer

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  • Frank
    Lv 7
    1 decade ago
    Favorite Answer

    Some hot tea has cooled from 95℃ to 23℃. Calculate the energy released in joules(J) if the sample of tea has a mass of 50.0g . Assume that the tea has the same specific heat(比熱) as water, 1.00 cal/g℃.

    解:  H=50*1*(95-23)=3600 cal

     因1 cal=4.18 J,所以3600 cal=15048 J,大約為15000 J

      

    What is the heat energy in joules released when 15.0 g of gold cools from 215℃to 35℃?

    解:  H=15*0.0309*(215-35)=83.4 cal

     因1 cal=4.18 J,所以83.4 cal=348.7 J,大約為350 J

      

    An ice cube tray is filled with 125 g of water and placed in a freezer. How many joules of heat are removed by the freezer compartment to form ice cubes at 0℃.

    解:  H=125*80=10000 cal

     因1 cal=4.18 J,所以10000 cal=41800 J,大約為42000 J

      

    When 0.02 oz of a milk-chocolate candy bar undergoes combustion in a calorimeter, the temperature of 500.0 g of water rises from 18℃ to 76℃. How many kilocalories are available in 1.00 oz of milk chocolate?

    解:  H=500*1*(76-18)=2900 cal

        2900*1/0.02=145000 cal=145 Kcal

         Ans: 大約為150 kcal。

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