Calculate the pH after 10.0 mL of 0.125 M NaOH is added to 30.0 mL of 0.105 M HCHO2.
Answers
Answer:
(a) Total number of moles present in 10 mL of 0.2 M calcium hydroxide are
1000
10×0.2
=0.002 moles.
Total number of moles present in 25 mL of 0.1 M HCl are
1000
25×2
=0.0025 moles.
Ca(OH)
2
+2HCl→CaCl
2
+2H
2
O
1 mole of calcium hydroxide reacts with 2 moels of HCl.
0.0025 moles of HCl will react with 0.00125 moles of calium hydroxide.
Total number of moles of calcium hydroxide unreacted are 0.002−0.00125=0.00075 moles.
Total volume of the solution is 10+25=35 mL.
The molarity of the solution is
35
0.00075×1000
=0.0214M
[OH
−
]=2×0.0214=0.0428M
pOH=−log0.0428=1.368
pH=14−pOH=14−1.368=12.635
(b) Total number of moles present in 10 mL of 0.01 M H
2
SO
4
is
1000
10×0.01
=0.0001 mol.
Total number of moles present in 10 mL of 0.01 M Ca(OH)
2
=
1000
10×0.01
=0.0001 mole.
Ca(OH)
2
+H
2
SO
4
→CaSO
4
+2H
2
O
0.0001 mole of Ca(OH)
2
will react completely with 0.0001 mole of H
2
SO
4
.
Hence, the resuting solution is neutral with pH 7.0
(c) Total number of moles in 10 mL of 0.1 M H
2
SO
4
=
1000
10×0.1
=0.001 mole.
Total number of moles present in 10 mL of 0.1 M KOH =
1000
10×0.1
=0.001 mole.
2KOH+H
2
SO
4
→K
2
SO
4
+2H
2
O
2 moles of KOH reacts with 1 mole of H
2
SO
4
.
0.001 mole of KOH will react with 0.0005 mole of H
2
SO
4
.
Number of moles of H
2
SO
4
left =0.001−0.0005=0.005M
Volume of solution is 10+10=20mL
Molarity of the solution is
20
0.0005×1000
=0.025M.
[H
+
]=2×2.5×10
−2
=0.05M
pH=−log[H
+
]=−log0.05=1.3.
Video Explanation
Solution to Question ID 423367
play-icon
Was this answer helpful?
upvote
43
downvote
1
SIMILAR QUESTIONS
star-struck
Write a short note on pH of pure water and its properties.
Easy
View solution
>
An aqueous solution of NaCl containing 5.85 g/L of NaCl was electrolysed by using platinum electrodes. Hydrogen and chlorine gases evolved at the cathode and anode respectively. Calculate the pH of the solution after electrolysis assuming complete electrolysis of NaCl.
Medium
View solution
>
View more
MORE FROM CHAPTER
Equilibrium
View chapter
>
PRACTICE FROM:
JEE Mains Questions
4 Qs
>
JEE Advanced Questions
7 Qs
>
NEET Questions
1 Qs
>
AIIMS Questions
1 Qs
>
BITSAT Questions
4 Qs
>
Easy Questions
8 Qs
>
SHORTCUTS & TIPS
Mindmap
Mindmap
1 min read
>
Common Misconceptions
Common Misconceptions
3 min read
>
Important Diagrams
Important Diagrams
4 min read
>
Problem solving tips
Problem solving tips
3 min read
>
Cheatsheets
Cheatsheets
2 min read
>
Enjoy a better experience
Scan a question with Toppr Answr app and find verified solutions