AQA AS Chemistry 2017 Paper 1 Titration MCQ Q16

Watch
xxccvc
Badges: 4
Rep:
?
#1
Report Thread starter 1 month ago
#1
25.0 cm3 samples of NaOH solution were taken by pipette from a beaker. These were then titrated with an aqueous solution of ethanoic acid. The concentration of ethanoic acid calculated from the experimental results was found to be lower than the actual value.


Which of these could explain the difference?


A Rinsing the pipette with distilled water before filling with NaOH
B Rinsing the burette with distilled water before filling with ethanoic acid
C Rinsing the walls of the conical flask with distilled water during the titration
D Rinsing the beaker with distilled water before filling with NaOH

[1 mark]

Could anyone please explain why the answer is B and explain why.
0
reply
Hellllpppp
Badges: 14
Rep:
?
#2
Report 1 month ago
#2
A Rinsing the pipette with distilled water before filling with NaOH
-This would dilute the NaOH. This has no effect on the moles of NaOH that must be neutralised by the ethanoic acid.

B Rinsing the burette with distilled water before filling with ethanoic acid
-This dilutes the ethanoic acid meaning a larger volume is required to neutralise the NaOH this increases the mean titre reading. The mean titre reading is then used to calculate concentration (moles/volume). As volume is larger the calculated concentration is smaller.

C Rinsing the walls of the conical flask with distilled water during the titration
-same reasoning as A

D Rinsing the beaker with distilled water before filling with NaOH

-same reasoning as A
0
reply
xxccvc
Badges: 4
Rep:
?
#3
Report Thread starter 1 month ago
#3
(Original post by Hellllpppp)
A Rinsing the pipette with distilled water before filling with NaOH
-This would dilute the NaOH. This has no effect on the moles of NaOH that must be neutralised by the ethanoic acid.

B Rinsing the burette with distilled water before filling with ethanoic acid
-This dilutes the ethanoic acid meaning a larger volume is required to neutralise the NaOH this increases the mean titre reading. The mean titre reading is then used to calculate concentration (moles/volume). As volume is larger the calculated concentration is smaller.

C Rinsing the walls of the conical flask with distilled water during the titration
-same reasoning as A

D Rinsing the beaker with distilled water before filling with NaOH

-same reasoning as A

So diluting has no effect on moles because:

If you dilute volume increases and concentration decreases

Due to n = c x v it has no effect on moles?
0
reply
Hellllpppp
Badges: 14
Rep:
?
#4
Report 1 month ago
#4
(Original post by xxccvc)
So diluting has no effect on moles because:

If you dilute volume increases and concentration decreases

Due to n = c x v it has no effect on moles?
Yeah moles of a specific element just represents the amount of atoms of that element so adding water doesn’t change that.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Have you experienced financial difficulties as a student due to Covid-19?

Yes, I have really struggled financially (83)
18.61%
I have experienced some financial difficulties (125)
28.03%
I haven't experienced any financial difficulties and things have stayed the same (166)
37.22%
I have had better financial opportunities as a result of the pandemic (58)
13%
I've had another experience (let us know in the thread!) (14)
3.14%

Watched Threads

View All
Latest
My Feed