Question

A sample has a hydrogen ion concentration of 1 × 10−2. What happens if the hydrogen ion concentration increases?

The acidity decreases.

The pH decreases.

The hydroxide ion concentration increases.

The solution becomes more basic.

Answer 1

If you had to make a guess what would you say?

Answer 2

i dont know

Answer 3

Okay then lets look at each option:

"acidity" is a measure of the tendency of a compound to give up a proton

pH is define as: pH=-log([H])

For hydroxide ions there the following relation: Cv= [H+] * [OH-]. Here is Cv a constant.

For a solution to become more basic the pH would have to increases.

Answer 4

So lets look at the cases:

The more acid a solution is the more [H] there will be so we can remove the first option.

pH=-log[H]
So lets take a look if we have a increase (10^-2<10^-1)
pH=-log(10^-2)=2
pH=-log(10^-1)=1

Cv=[H+] * [OH-] <-> [OH-]=Cv/[H+]... we know from math that when the denominator is geting higher the fraction get lower.

We just saw that the pH does not increases.

So what answer is it?

Answer 5

The hydroxide ion concentration increases.
as if u increase H+ concentration along that there i a buffer in water which balances H+ and OH- ion concentration

Answer 6

Disagree, as you violate the self-ionization of water then.

Answer 7

but der is a property of buffer too what about dat?

Answer 8

We don't know if it is a buffer solution only that the concentration of protons incresse. No where in the question we are told that the acid along with its conjugated base is present.

Answer 9

hmm...

Answer 10

But lets assume the following:
as I also say water will self-ionization so we set up the following equation:
\[Cw=[H _{3}O ^{+}]*[OH ^{-}]\]
Cw is the self-ionization constant
\[Cw=[H _{3}O ^{+}]*[OH ^{-}] <-> [OH ^{-}]=\frac{ Cw }{ [H _{3}O ^{+}] }\]

What happens when H3O+ increases?

Answer 11

OH- io concentration decreases

Answer 12

Exactly :)

Answer 13

mean Cw decreases

Answer 14

Cw is constant.

Answer 15

It is only dependent on tempeture and such.

Answer 16

how?
because in the same amount H3O|+ increases as in the same amount of OH- ion deacreses u see..

Answer 17

thats why the equation u mention is right and such condition prooves that cw is constant

Answer 18

That is right and is therefore the argument for the option "The hydroxide ion concentration increases." is wrong :)

Answer 19

but according to the option if u see the most probable ans it will be hydroxide ion concentration increases

Answer 20

Why not the option "the pH decreases"?

Answer 21

yes u are right my mistake the ans will be pH decreases

Answer 22

:)