tvd7 Posted April 21, 2008 Report Share Posted April 21, 2008 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 Link to post Share on other sites More sharing options...
Mandiloquence Posted April 21, 2008 Report Share Posted April 21, 2008 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 LOSTWell, 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! Link to post Share on other sites More sharing options...
IBStuck Posted April 22, 2008 Report Share Posted April 22, 2008 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. Link to post Share on other sites More sharing options...
IBStuck Posted April 24, 2008 Report Share Posted April 24, 2008 well you asked so here it is.Titration_Notes.doc Link to post Share on other sites More sharing options...
Max Posted April 25, 2008 Report Share Posted April 25, 2008 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. Link to post Share on other sites More sharing options...
IBStuck Posted April 26, 2008 Report Share Posted April 26, 2008 we never did that. we just did the meathod tat is in my notes. Link to post Share on other sites More sharing options...
booji Posted June 16, 2008 Report Share Posted June 16, 2008 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! Link to post Share on other sites More sharing options...
Mahuta ♥ Posted May 15, 2011 Report Share Posted May 15, 2011 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 Link to post Share on other sites More sharing options...
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