33Mujhe .."which indicator to use" me bahut din se doubt hai... :(
Consider a pH titration of 50 mL 0.1 M benzoic acid vs 0.1M NaOH at 25°C. The experimentally observed curve is shown below, on which points A, B, C…… F are marked.
a) Which point corresponds to approximately 0.07 M
benzoic acid solution?
b) Suppose you are carrying out a conventional titration of benzoic acid and NaOH. Using choose an appropriate indicator from the table below.the answer obtained
Indicator pH range Colour change
Methyl yellow 2.9 - 4.0 red-yellow
Methyl orange 3.1 – 4.4 red-orange
Phenolphthalein 8.0 - 9.8 colorless-red
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UP 0 DOWN 0 0 39
39 Answers
33
1357To find the equivalence point Phenolphthalein should be used as seen from the curve
33We have to use such indicator... (whose range includes..neutral point ph=7).. am i right..??
1357@ priyam....a little mistake...be careful with this
let the volume added be V
milliequivalent of acid =5
milliequivalent of NaOH =0.1*V=V/10
remaining meq of acid=5-V/10
total volume=V+50
(5-V/10)/(V+50)=0.07=7/100
500V-10V=7V+350
17V=150
V=9 ml
33Q.1 Point B.
Benzoic acid is taken in flask and then NaOH is added..
Now 0.07 M benzoic acid means... 0.03(50) M.eq is used up by NaOH..
M.eq of NaOH=0.03(50)
0.1(v)=1.5
V=15ml NaOH
so point B
33@manish bhaiya
hmm.... lekin issse koi point nahi aa raha q me....
1357For second one
at volume of 50 ml pH=7
if you add 1 drop more the pH becomes 9 etc.
so you will be able to see the change in colour of indicator
21tapanmast
#3 Posted 10:41pm 16-03-09
Re: definitely a QOD...
USE PHENOLPHTHALEIN
33Phenolphthalein 8.0 - 9.8 colorless-red
means
Phenolp is colorless for pH<8
and red for pH>9.8
1357part b seems incomplete because it is not asking for the equivalence point
I think there is something missing from the question
please find it
1357I saw the Incho paper
they are asking for the half equivalence point
now try guys
13yes MATRIX it is
i noe ppl lyk u never go wrong
but bro post d soln 2 and hv a luk at second ques
13yes it is .....
explaination de de mere bhai
dis ques wasnt meant for ur practic but was my doubt