Use the concentrations of [H_3O^+] and [OH^-] to calculate the missing concentra
ID: 486605 • Letter: U
Question
Use the concentrations of [H_3O^+] and [OH^-] to calculate the missing concentration and indicate whether the solution is acidic or basic In order to make it easier to comprehend, [H_3O^+] and [OH^-] are often expressed as pH and pOH respectively. The symbol p in front of any quantity means *negative logarithm of e.g., pKa would be defined as pKa = -log Ka. The relationship between pH and pOH can be derived from K_w as follows Taking the negative log on both sides we have Recall that log ab = log a + log b pH 7 is basic [H_3O^+] from pH and [OH^-] from pOH. You can convert from pH and pOH to the concentrations of [H_3O^+] and [OH^-] usingExplanation / Answer
Ans. For pure water- ; [ all concentrations in term of molarity]
[H3O+] x [OH-] = 10-14
[H+] = [OH-] = 10-7
So,
[H3O+] = (10-14) / [OH-]
[OH-] = (10-14) / [H3O+] ; H+ and H3O+ mean the same.
When,
I. [H+] in solution in > 10-7, it is acidic. Neural water has [H+] = 10-7, so pH lowers or become more acidic when [H+] becomes greater than 10-7.
II. [OH-] in solution in > 10-7, it is basic.
III. [H+] increase with decrease in [OH-]. So, [H+] less than 10-7 also indicates basic solution. Ans, [OH-] less than 10-7 indicates acidic pH.
[H3O+]
[OH-]
Acidic / Basic
(10-14) / (3.2 x 10-6) = 3.12 x 10-8
3.2 x 10-6
Basic
4.8 x 10-3
(10-14) / (4.8 x 10-3) = 2.08 x 10-12
Acidic
(10-14) / (7.4 x 10-8) = 1.35 x 10-7
7.4 x 10-8
Acidic
2.1 x 10-9
(10-14) / (2.1 x 10-9) = 4.76 x 10-6
Basic
Let’s compare “ 1.35 x 10-7 ” – result 3
[H+] in neutral water = 10-7 = 0.0000001 = 0.000000100
[H+] in solution 3 = 1.35 x 10-7 = 0.000000135
Since, 0.000000135 > 0.000000100 , the solution has higher [H+] than pure water. Thus, this solution is acidic.
[H3O+]
[OH-]
Acidic / Basic
(10-14) / (3.2 x 10-6) = 3.12 x 10-8
3.2 x 10-6
Basic
4.8 x 10-3
(10-14) / (4.8 x 10-3) = 2.08 x 10-12
Acidic
(10-14) / (7.4 x 10-8) = 1.35 x 10-7
7.4 x 10-8
Acidic
2.1 x 10-9
(10-14) / (2.1 x 10-9) = 4.76 x 10-6
Basic
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