[EX5TASY]

Consider the following reaction.

2 HCl(aq) + Ba(OH)2(aq) BaCl2(aq) + 2 H2O(l)  deltaH = -118 kJ

Calculate the heat when 110.0 mL of 0.500 M HCl is mixed with 300 mL of 0.430 M Ba(OH)2. Assuming that the temperature of both solutions was initially 25.0°C and that the final mixture has a mass of 410 g and a specific heat capacity of 4.18 J/°Cg, calculate the final temperature of the mixture.



I'm confused on this problem... does the # of Moles of the reactants matter? THe way I have been doing it according to previous examples is

Heat evolved = (Specific Heat Capacity) x Mass of Soln x Increase in Temperature
Thereby,

118000J = (4.18J/°Cg) x 410g x (T)

Solve for T to get 201.64

Then find the change in temperature to be
x - 25 = 201.64,  X = 226.64°C

But this answer is wrong... can someone help me?

[_cheers]

I'm not sure if I'm much help, but isnt the value T the change in T? and not just T? then you would have an unknown variable Tf? and yes, I do believe there is something to do with moles....but hmmm...which moles....

someone correct me if I'm wrong, but thats how I would think about it.

Cheers

[allanf]

yes the number of moles of reactants matters a lot.  Enthalpies are extensive, they scale with the number of moles.  What you should first do is figure out what the limiting reagent is, this tells you how much of the reaction will happen assuming it proceeds 100%.

[_cheers]

yeah! thats what I was trying to say 

[EX5TASY]

I'm still not understanding... can someone walk me through it pleaseee?

 

[EX5TASY]

nevermind, i think I've got it now

[thegoodaaron]

I'm confused with this problem, too. How did you solve it, EX5TASY? I can't seem to figure out how to include the number of moles in the calculation.

EDIT: I got it!