# HELP! Titration calculations

## Recommended Posts

Help me!!!

I've done a thermometric titration calculation of HCl against NaOH and CH3COOH against NaOH...my final results gave me the volumes i used (cm3), the temperature change of the mixture throughout the titration, and the peak temperature of each titration.

In other words, we are meant to find the concentration and enthalpy change of neutralization of each acid. Normally, this would be really easy, but how am I supposed to calculate the number of moles of each acid if i only know the volume and mass number of each?

Does the volume become the mass? aghhhh I'M SO LOST

##### Share on other sites
Help me!!!

I've done a thermometric titration calculation of HCl against NaOH and CH3COOH against NaOH...my final results gave me the volumes i used (cm3), the temperature change of the mixture throughout the titration, and the peak temperature of each titration.

In other words, we are meant to find the concentration and enthalpy change of neutralization of each acid. Normally, this would be really easy, but how am I supposed to calculate the number of moles of each acid if i only know the volume and mass number of each?

Does the volume become the mass? aghhhh I'M SO LOST

Well, I haven't done the acids and bases section yet (that's our next chapter), so I don't know how much this will help you...

but isn't concentration normally given in Molarity, which has units of moles per volume? And you can obtain moles from mass if you have a periodic table...and I'm fairly sure that you can calculate enthalpy change using Hess's law.

Anyway, I hope that helps a little. Good luck!

##### Share on other sites

i think i have some tirtration examples typed up with notes, but i cannot promise then to be 100% clear. do you want me to load them up here? PM if you want me to.

##### Share on other sites

well you asked so here it is.

Titration_Notes.doc

##### Share on other sites

Hah, that's what we just did (I used the same acids and the same base btw. )

Are you sure you don't know the concentration of either substance? As far as I know, (correct me if I'm wrong, since I'm sometimes doubtful about my knowledge of Chemistry ) the point of a titration is to add a solution of known volume and concentration to a solution of known volume but unknown concentration

If you know the number of moles you can then use the equation

q = mcΔT

where q is the heat energy (in J), m the mass of the substance (in grams), c the specific heat capacity (I used 4.18, which happens to be the heat capacity of water) and ΔT the change in temperature.

After you find q, you divide it by the number of moles to get the enthalpy change in J/mol.

##### Share on other sites

we never did that. we just did the meathod tat is in my notes.

##### Share on other sites
we never did that. we just did the meathod tat is in my notes.

Assuming you standardized your NaOH solution, you will know exactly how much NaOH was required at neutralization (in volume). By standardization, you will have the exact concentration. Since concentration is simply the ratio of moles to volume in dm3, the moles of NaOH can be caluclated. Since the neutralization of a monoprotic strong acid with NaOH occurs in a 1:1 stochiometric ration, the moles of NaOH should equal the moles of HCl. This you can then use in the MCAT formula (Q=mc/_\T) to calculate the heat change.

For a weak acid, it becomes just a little more difficult since you have to account for the amount of non-dissociated acid. Thus for the weak acid, I would just recommend setting up an initial, equlibirum, and final table, and use variables to calculate the change. This is a little difficult to type out, so if you have a question feel free to PM me and I can send you a scanned copy of how to do this.

Good Luck!

##### Share on other sites

Automatic generated message

This topic has been closed by a moderator.

Reason: Revived after 3 years.

If you disagree to this action, please report this post, and a moderator or administrator will reconsider it.

Kind regards,

IB Survival Staff