APPLICATION QUESTION ON pH CALCULATION.

INSTRUCTION:- show your working and post your answer into the COMMENT OR JOIN DISCUSSION BOX below the question.

 

 

QUESTION

A tribasic acid recorded 3 on the screen of a pH meter when analyzed, calculate the molarity of the acid.

 

(A). 0.02

 

(B). 0.04

 

(C). 0.09

 

(D). None

 

 

 

 

Goodluck…

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Chidocks
Chidocks
June 24, 2020 8:53 pm

Chidocks
Answer: (D) None

Reason:
Tribasic Acid implies → 3H^+
pH = 3
Formula: pH = -log(H+) Note Log is to base 10

Substitute (H^+) for (3H^+) as we are dealing with a tribasic acid
3 = -log (3H^+)
Just switch
-log (3H^+) = 3
log (3H^+) = -3
(3H^+) = {10^-3} ÷ {3}
(H^+) = 0.00033
Therefore, Molarity = 0.0003 {4d.p}

Edmond
Edmond
January 15, 2021 5:42 am
Reply to  Chidocks

Nice work

Daniel
Daniel
June 25, 2020 12:02 am

A tribasic acid has three hydrogen atoms hence
[3H^+]
pH is given As 3
pH = -log[3H^+]
3 = -log[3H^+]
Log[3H^+] = -3
[3H^+]= 10^-3
H^+ =0.001/3
H^+ = 0.003mol per dm^3
Hence the answer is D(none)

Daniel
Daniel
June 25, 2020 12:03 am
Reply to  Daniel

0.0003 mol per dm^3 as main answer

Godstime
Godstime
June 25, 2020 1:49 am

The answer is D

PH = -log [H^+]

3 = – log 3[H^+]

3[H^+] = 1/10^3

[H^+] = 1/3000

[H^+] = 3.3×10^4 = 0.00033mol/L

Clyde
Clyde
June 25, 2020 7:20 am

Let the molarity be x
From the formula we understand that
pH= -log(H+)
Sub…
We’ve….
3= -log(3x)
In3 = 3x

1.0986 = 3x
x =0.366M

Uchenna Stephen
Uchenna Stephen
June 25, 2020 11:14 am

pH = 3
Tribasic acid = 3H^+

Formula for pH = – Log(H^+)

=> – log(3H^+) = 3
=> log(3H^+) =-3
3H^+ = 10^-3
3H^+ = 0.001
H^+ = 0.0003M

D. (None)

Onyi
Onyi
June 26, 2020 2:07 pm

pH= -log(H+)
pH = 3
10^3=1\H+
Therefore H+ = 1\1000= 0.001
Ans= D

Mira_Gem
Mira_Gem
June 30, 2020 4:07 am

Answer is D.
Using calculator method,
pH = -log[H+]
-log[H+] = pH
-log[H+] = 3
H+ = (antilog, 10^-3, I.e, the 2nd function on the log key on the calculator,(i.e that of 10^x which is antilog of the number. Press shift button and then log button followed by the negative sign button (-), followed by the number, in this case, 3, which will appear as -3 in advanced scientific calculator).
[H+] = 10^-3
= 1×10^3.

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