If the ph of a 0.2 m solution of weak base is 10.3 then find the volume of hcl solution
Answers
Answer:
p
H
=
2.69897000434
Explanation:
It is a strong acid-base reaction as HCl is a strong acid and Ca(OH)2 is a strong base
Ca(OH)2+HCl=CaCl2+2H
2
O
The net ionic reaction is
H
+
(
a
q
)
+
O
H
−
(
a
q
)
=
H
2
O
(
l
)
The number
H
+
ions in the solution is the concentration of HCl because strong acids dissociate completely thus producing
1mole of H+
1mole of acid.
This is only applicable to strong acids. The same is the case with strong base but instead of
H
+
they produce strong conjugate bases like
O
H
−
HCl is a strong acid thus
moles of HCl = moles of
H
+
Calculate no. of moles in 30mL of 0.01M HCl
L
⋅
M
=
moles
30
⋅
10
−
3
L
⋅
0.01
=
0.0003moles
0.0003moles of HCl will produce 0.0003moles of
H
+
Now calculate the number of moles in 20mL of 0.01M
C
a
(
O
H
)
2
solution.
C
a
(
O
H
)
2
i
s
a
s
t
r
o
n
g
b
a
s
e
t
h
u
s
moles of
C
a
(
O
H
)
2
= moles of
O
H
−
20
⋅
10
−
3
L
⋅
0.01
M
=
0.0002moles
0.0002moles of
C
a
(
O
H
)
2
= 0.0002moles of
O
H
−
As this is titrating of a strong acid with a strong base the addition of the base results in decrease in
H
+
ions. I mol of OH- results in decrease of 1 mol of H+
0.0003mole - 0.0002mole = 0.0001mole of
H
+
You must now calculate the pH by using the moles and the total volume
But while calculating pH we must use the molarity and not mole.
For that we need to add both the volumes that is
20mL + 30mL = 50mL = 0.05L
0.0001mole
0.05L
=
x
1
L
=
0.002
1
L
= 0.002M of
H
+
p
H
=
−
log
(
H
+
)
p
H
=
2.69897000434
if you are satisfy with my ans then mark me as a brainlist
if there is something wrong then kindly rectify it