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## #1 2013-05-30 02:35:21

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,851
Website

### potenz Hydrogen

Calculate the pH of of 0.002 m of H[sub]2[/sub]SO[sub]4[/sub]

I do not even understand what m means

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #2 2013-05-30 02:35:59

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: potenz Hydrogen

It means molar does it not?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #3 2013-05-30 03:58:12

bob bundy
Registered: 2010-06-20
Posts: 8,337

### Re: potenz Hydrogen

hi Agnishom,

0.002m means the concentration of H2SO4 in moles per cubic decimetre.

It's a strong acid so it is fully dissociated in water => the concentration of hydrogen ions is 0.002 x 2 = 0.004 (as it's H2.....)

The pH is then given by

Hope that helps,

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #4 2013-05-30 17:10:40

barbie19022002
Member
Registered: 2013-05-24
Posts: 1,314

### Re: potenz Hydrogen

H2SO4 means sulphuric acid...right..

Jake is Alice's father, Jake is the ________ of Alice's father?
Why is T called island letter?
think, think, think and don't get up with a solution...

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## #5 2013-05-30 17:36:46

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,851
Website

### Re: potenz Hydrogen

Yes, thats sulphuric acid.

Bob, does hydrogen concentration equal to that m number times the number of molecules of H
If that is so, I wanted to post another problem

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #6 2013-05-30 17:47:32

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,037

### Re: potenz Hydrogen

Hi Agbishom

It seems to be so.

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #7 2013-05-30 18:27:03

bob bundy
Registered: 2010-06-20
Posts: 8,337

### Re: potenz Hydrogen

hi Agnishom

does hydrogen concentration equal to that m number times the number of molecules of H

Yes, it does.  Post your problem.

A cautionary tale:

There once was a student from Lahore,
Said: "I need a drink,  that's for sure",
His error was a blow,
What he thought was H2O,
Was actually H2SO4.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #8 2013-05-30 18:57:15

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,851
Website

### Re: potenz Hydrogen

Calculate the pH of a solution which consists of 0.01 m of KOH and 0.02 of HNO[sub]3[/sub]

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #9 2013-05-30 18:57:41

barbie19022002
Member
Registered: 2013-05-24
Posts: 1,314

### Re: potenz Hydrogen

Oh my god...he though sulphuric acid was water...very funny..

Jake is Alice's father, Jake is the ________ of Alice's father?
Why is T called island letter?
think, think, think and don't get up with a solution...

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## #10 2013-05-30 19:29:55

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,851
Website

### Re: potenz Hydrogen

Why did he think so?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #11 2013-05-30 19:43:57

bob bundy
Registered: 2010-06-20
Posts: 8,337

### Re: potenz Hydrogen

Why did he think so?

Both colourless liquids.  Always read the label!

Calculate the pH of a solution which consists of 0.01 m of KOH and 0.02 of HNO3

These two react and there may be some acid or alkali left at the end to give a pH.  But without knowing the amount of each in the solution you cannot figure that out.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #12 2013-05-30 19:49:17

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,851
Website

### Re: potenz Hydrogen

that's a point. I will try to look for the exact question

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #13 2013-05-31 06:33:51

bob bundy
Registered: 2010-06-20
Posts: 8,337

### Re: potenz Hydrogen

I have consulted with my resident chemist.  The problem is far from straight forward even when you know the two volumes.

For simplicity, let's say there are equal amounts of each.

The 0.01 and 0.02 mean that both are dissolved in water to give those concentrations.  If equal amounts are mixed together they will react.  One molecule of KOH with react with one molecule of HNO3 to give KNO3 and H2O.  So now there is extra water.

Only half the acid will react because of the different concentrations.  The remaining acid is now much more dilute (i) because of the water the alkali was dissolved in and (ii) because of the water generated by the reaction.  I'm still waiting for a response about what the concentration now is.  eg.  If there was 100 ccs of acid and 100 ccs of alkali, then that's 200 ccs due to (i) and what? due to (ii).

LATER EDIT:

The oracle says ignore (ii).  Cannot establish whether that's because it is negligible or because of some strange molar argument but anyway that makes life simpler.

We then have 0.02 becomes 0.01 because of the reaction, and then 0.005 because of (i).

So the answer would be -log(0.005).

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #14 2013-05-31 08:57:30

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,037

### Re: potenz Hydrogen

Hi Bob

I love the poem, but I find this versuon better:
"Little John was very thirsty,
Now he is no more,
For what he thought was H2O
Was H2SO4"

I think it gets worse if we change 'thought' to 'taught'.

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #15 2013-05-31 09:17:00

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: potenz Hydrogen

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #16 2013-05-31 19:12:04

bob bundy
Registered: 2010-06-20
Posts: 8,337

### Re: potenz Hydrogen

Thanks Stefy,

That's the poem I was trying to remember.  But I thought it was a limerick.  I made that one up myself.  I'll abandon poetry and stick to maths in future.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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