Weak acid and weak alkali

Question

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

and alkali??????

Temperature change?????

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

Answer 1

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

Answer 2

Joyce.....好心你啦......

Answer 3

agree with 樓上,,

只有 003 ge 答案是 correct

Answer 4

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

Answer 5

Do titration可以 detect the end point of neutralization

D indicator 樓上有人講左

Answer 6

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

001 ge答案唔係太好...