boiling point

how does the amount of salt added change the boiing point of water?

10g/20g/30g/40g...

the tenperture will higher or lower?

need expend...

(should use chinese and english to answer)

3 個解答

評分
  • 土扁
    Lv 7
    10 年前
    最愛解答

    A solution is formed when salt is dissolved in water. The boiling point of the solution formed will be higher than that pure water. This is known as "boiling point elevation".

    The more the salt added, the higher the boiling point of the solution is.

    Mathematically, ΔTb = 0.512mb

    where ΔTb = elevation in boiling point (°C) = (boiling point of solution) - (boiling point of pure water)

    and mb = molality of ions in the solution = (no. of moles of ions) / (1 kg of water)

    當鹽加入水中,形成溶液。溶液的沸點較純水的沸點高。這稱為「沸點上升」。

    所加入的鹽愈多,溶液的沸點愈高。

    數學上,ΔTb = 0.512mb

    其中 ΔTb = 沸點上升 (°C) = (溶液的沸點) - (純水的沸點)

    而 mb = 溶液中離子的重量摩爾濃度 = (離子的摩爾數) / (1 kg 的水)

    reference (參考資料):

    http://en.wikipedia.org/wiki/Molality#Molality

    資料來源: 土扁
  • 10 年前

    在加入 salt 而令 boiling point of water 上升的課題上,教科書習慣用 solvent 或 water,其實是指加入了 salt 的 water,其意是指 solution。因為加入 salt 之前是 water,所以加了 salt 之後仍然用 water 這個字,方便對比。

    2010-12-02 17:04:11 補充:

    例如維基百科 http://en.wikipedia.org/wiki/Boiling-point_elevati... 中:

    "Boiling-point elevation describes the phenomenon that the boiling point of a liquid (a solvent) will be higher when another compound is added……"

    (這段是抄自教科書的。)

    2010-12-02 17:04:30 補充:

    這裡的 solvent,是 water,boiling-point elevation 的其實是已加了 salt 的 solution,但字面還是用 solvent 或 water,原因如上。相信土扁用 solution 只是想令更忠於事實而已。

    不要自作聰明的逐字翻譯,把全世界的教科書都說成錯誤,把科學題目變成了捉字虱的無聊 I.Q. 題。

    2010-12-04 16:30:23 補充:

    對不起,是我的語氣過重了。

  • there will be no change to the boiling water, it remains 100 degree C.

    水既沸點係唔會變,只會維持於攝氏100度。

    2010-12-01 16:46:57 補充:

    土扁, 人地問boiing point of water 唔係boilng point of solution 呀!就算你加幾多salt 落去,boilng point of water 都依然唔會changed, 都依然係100度GA!

    2010-12-03 19:23:48 補充:

    Sor,小人無知,而且無意亦唔敢亦無能力挑戰全世界的教科書。

    資料來源: 物理定律
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