[kimxx972]

Cresol red indicator has two color changes in the pH range 0-14.
pH range       acid color      base color
0.2-1.8            red              yellow
7.2-8.8           yellow             red

What colors are to be expected in solutions at pH values of 1.0, 6.0 and 9.0?

                1.0              6.0               9.0
(A)            Red            Red              Yellow
(B)            Red            Yellow          Yellow
(C)            Orange       Yellow          Red
(D)            Yellow        Orange         Red
(E)            Red            Red              Orange

The ans is (C).

Can anybody explaing why the answer is C ?

Thank you

[nj_bartel]

pH 1 is between 0.2 and 1.8.  You blend red and yellow to get orange.  pH 6 is between 1.8 and 7.2.  You're in the yellow range of both indicators.  pH 9 is above 8.8 and is thus in the red range.

[Borek]

More quantitative discussion:

http://www.titrations.info/acid-base-titration-indicators

[kimxx972]

Thanks for your simple but understandable explanation.

The website is also very helpful to catch up the definition of titration.

[hey chikitha]

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[jag300]

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When will be the results out of nov 7 chem gre...
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