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1. Mole, Concentration and Volume calculations
I'm stuck on this question:

What is the volume, in cm^3, of 0.25 mol dm^–3 hydrochloric acid required to neutralise 100 cm^3 of 0.125 mol dm^–3 barium hydroxide solution, Ba(OH)2(aq)?

Here's all the given information put simply:

Ba(OH)2
Concentration = 0.125 mol dm-3
Volume = 100 cm3
Moles = ?

HCl
Concentration = 0.25 mol dm-3
Volume = ?
Moles = ?

Presumably you have to use the Moles = Concentration x Volume formula.

It seems pretty simple, but I got an answer of 0.05, and the answer booklet says it's 100cm^3. I guess I'm going wrong either working out the ratio or converting units. Can anybody help?
Last edited by Student141; 29-12-2010 at 21:09. Reason: Formatting
2. Re: Mole, Concentration and Volume calculations
(Original post by Student141)
I'm stuck on this question:

What is the volume, in cm^3, of 0.25 mol dm^–3 hydrochloric acid required to neutralise 100 cm^3 of 0.125 mol dm^–3 barium hydroxide solution, Ba(OH)2(aq)?

Here's all the given information put simply:

Ba(OH)2
Concentration = 0.125 mol dm-3
Volume = 100 cm3
Moles = ?

HCl
Concentration = 0.25 mol dm-3
Volume = ?
Moles = ?

Presumably you have to use the Moles = Concentration x Volume formula.

It seems pretty simple, but I got an answer of 0.05, and the answer booklet says it's 100cm^3. I guess I'm going wrong either working out the ratio or converting units. Can anybody help?
Firstly, you need to work out the moles of Ba(OH)2 - have you done that? Quite rightly as you've mentioned therefore

Once you have this you can then use the moles with the concentration of HCl in order to find its volume; since it doesn't specify a formula for HCl, you can assume the moles are the same.

Also, I have a feeling you've forgotten to convert the volume of Barium Hydroxide into In this case should do the trick.

Didn't know I was capable of providing an answer for Chemistry.
Last edited by Femto; 29-12-2010 at 21:17.
3. Re: Mole, Concentration and Volume calculations
i know you posted this 2 years ago but i'm going to answer anyway because i was stuck on it but in answering have just worked it out

1. First write out the equation: Ba(OH)2 + 2HCl --> BaCl2 + 2H2O
2. Find the moles of Ba(OH)2- 0.125 X (100/1000) (/1000 to get it to dm3 not cm3) = 0.0125
3. From the equation, one mole Ba(OH)2 reacts with 2 moles HCl, so there are twice as many moles of HCl as there are Ba(OH)2, so moles HCl=0.025
4. Volume HCl is moles/concentration so 0.025/0.25=0.1dm3
5. Convert to cm3 as that's what the question asks: 0.1 X 1000 = 100cm3