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Wai Yi asked in 科學及數學化學 · 1 decade ago

Weak acid and weak alkali

有什麼方法可以 detect the end point of neutralization between weak acid

and alkali??????

Temperature change?????

Thanks a lot!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

6 Answers

Rating
  • 1 decade ago
    Favorite Answer

    Use indicator:

    1. Methyl orange:

    In acid medium: red

    In alkaline medium: yellow

    2. Phenolphthalein:

    In acid medium: colourless

    In alkaline medium: pink

    End point: light pink

    Neutralization is an exothermic reaction.

    The reaction produces heat.

    The temperature of reaction mixture rises.

    But the temperature changes very slightly.

    It is not easy to measure it.

    2008-04-07 10:35:45 補充:

    睇漏左d野

    Commonly, we don't use waek acid and weak alkali to do titration,

    because there is no sharp change in pH at the equivalence point.

    Most indicators will not give a sharp colour change at the equivalence,

    but they will change colour gradually over a large volume of the acid or base added.

    2008-04-07 10:35:54 補充:

    You can refer to the titration curves

    http://www.chemguide.co.uk/physical/acidbaseeqia/s...

    Source(s): me
  • 1 decade ago

    Joyce.....好心你啦......

  • Jz
    Lv 4
    1 decade ago

    agree with 樓上,,

    只有 003 ge 答案是 correct

  • 1 decade ago

    For a neutralization between weak acid and weak alkali, no indicator is suitable for titration. At equivalence point, the pH will not vary greatly from pH 7 so no indicator is suitable for titration. We can use conductivity meter or the temperature probe to trace the end point of the neutralization.

    For neutralization between weak acid and strong alkali, the titration with phenolphthalein as indicator can be used to detect the end point because the equivalence point is greater than pH 7

    As I dun know which neutralization u are talking about, so I state both of the neutralization

    Hope can help u~

    2008-04-05 22:22:16 補充:

    sor, i just miss your title, is weak acid and weak alkali, just ignore the part for weak acid and strong alkali

    Source(s): myself
  • 1 decade ago

    Do titration可以 detect the end point of neutralization

    D indicator 樓上有人講左

  • 1 decade ago

    indicator 對weak acid weak alkali ge reaction無明顯ge反應...

    001 ge答案唔係太好...

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