JHYC Posted November 16, 2011 Report Share Posted November 16, 2011 This is the reaction I am indirectly findingCuSO4 + 5H2O --> CuSO4.5H2OThese are the two equations I am using to construct the Hess' cycle1. CuSO4 + xH2O --> CuSO4(aq)2. CuSO4.5H2O + xH2O --> CuSO4(aq)What should the coefficient of H2O be? Reply Link to post Share on other sites More sharing options...
Keel Posted November 16, 2011 Report Share Posted November 16, 2011 (edited) This is the reaction I am indirectly findingCuSO4 + 5H2O --> CuSO4.5H2OThese are the two equations I am using to construct the Hess' cycle1. CuSO4 + xH2O --> CuSO4(aq)2. CuSO4.5H2O + xH2O --> CuSO4(aq)What should the coefficient of H2O be?The x should represent an undetermined amount which is sufficient to turn the salt into a solution. In other words, so much that you can be sure that the solution is not going to be saturated. For example, a whole beaker of water. Fix how much CuSO4 you will use and estimate an appropriate volume.Remember the goal of the experiement. You are trying to find the enthalphy of the first equation through the enthalphies of the following two. Since you are measuring temperature, the value x is not a concern. Edited November 16, 2011 by Keel 2 Reply Link to post Share on other sites More sharing options...
JHYC Posted November 16, 2011 Author Report Share Posted November 16, 2011 Thanks dude! Hate to bother you but could you clarify?If I had say 0.01 mol of CuSO4 and I used 2 mol of water, would I have to write the equation as:CuSO4+ 200H2O----> CuSO4(aq)Because of the ratio? Or just leave it as x?Also, when I am trying to construct the cycle by rearranging the two equations, I have to somehow make a 5H2O on the reactant side, therefore, assuming that the first equation does use 200H2O, would I have to make the second equations reactant 195H2O?Im sorry but my teacher is obsessive over the tiniest details, she scrapped my entire last IA because a few words matched those in her mark-scheme...so...I would really appreciate some help Reply Link to post Share on other sites More sharing options...
Keel Posted November 16, 2011 Report Share Posted November 16, 2011 (edited) Thanks dude! Hate to bother you but could you clarify?If I had say 0.01 mol of CuSO4 and I used 2 mol of water, would I have to write the equation as:CuSO4+ 200H2O----> CuSO4(aq)Because of the ratio? Or just leave it as x?Also, when I am trying to construct the cycle by rearranging the two equations, I have to somehow make a 5H2O on the reactant side, therefore, assuming that the first equation does use 200H2O, would I have to make the second equations reactant 195H2O?Im sorry but my teacher is obsessive over the tiniest details, she scrapped my entire last IA because a few words matched those in her mark-scheme...so...I would really appreciate some helpLeave it as x. Because if you think about it, the number of moles of water does not affect the enthalphy change, the reaction will give out a finite amount of energy. The volume of water only affects the temperature change i.e. small volume, higher energy density, therfore higher temperature change; large volume, small temperature change.Leave both as x you are only interested in the energy change. Edited November 16, 2011 by Keel Reply Link to post Share on other sites More sharing options...
JHYC Posted November 16, 2011 Author Report Share Posted November 16, 2011 Ok dude, thanks so much, I really appreciate your help! You really saved my life!Cheers! Reply Link to post Share on other sites More sharing options...
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