wiz-icon
MyQuestionIcon
MyQuestionIcon
1
You visited us 1 times! Enjoying our articles? Unlock Full Access!
Question

pH of 0.1 M solution of NaA (sodium salt of a weak acid HA) is 8.92. Calculate pKa of HA. If a drop of HPh (pKin=9.52) be added to the above solution, predict whether the pink colour will visible or not under the medical fact that our eyes can see the pink colour if the mole % of ionized form of indicator is 25% or more.

A
Pink colour will be visible
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
B
Pink colour will not be visible
No worries! We‘ve got your back. Try BYJU‘S free classes today!
C
Cannot be predicted
No worries! We‘ve got your back. Try BYJU‘S free classes today!
D
None of the above
No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution

The correct option is C Pink colour will be visible
A+H2OHA+OH0.10.1xxx Kr
Kr=x20.1x=KwKHAa
KaHA=Kw(0.1xx2)
[pKa=lKwlog(0.1x)+2logx](1)
pH=logx=8.92 x=108.92
putting this in (1) & joining x in (0.1x)
as x<<0.1
pKa=pKwlog0.1+2logx
=148.92+1
=6.08
2nd part:
HPh+OHPH+H2O
PKin=9.52 Kin=Kaxn=109.52
Krxn=109.52=[Ph][H][OH][HPh][OH]
[Ph][HPh]=109.52+8.92
=100.6
0.2512>0.25
pink variable

flag
Suggest Corrections
thumbs-up
0
Join BYJU'S Learning Program
similar_icon
Related Videos
thumbnail
lock
Degree of Dissociation
CHEMISTRY
Watch in App
Join BYJU'S Learning Program
CrossIcon