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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: s3a on September 27, 2009, 11:29:06 PM

Title: Find the enthalpy of neutralization, ∆H , in kJ/mol
Post by: s3a on September 27, 2009, 11:29:06 PM
50.0 mL of 1.00 M HCl solution are mixed with 30.0 mL of 2.00 M NaOH solution in a coffee-cup
                                                                           o
calorimeter. The initial temperature of the solutions before mixing is 20.5 C. The highest
                                           o
temperature recorded after mixing is 29.8 C. The total mass of the solution is 80.5 g. Calculate
a) the heat change, q, in joules, accompanying this reaction and state whether the process is exo- or
                                                       o                               o
endothermic b) the enthalpy of neutralization, ∆H , in kJ/mol. ( swater = 4.184 J/g C )

Answers:
[ a) q = – 3,132.35 = –3.1 x 103 J = –3.1 kJ, exothermic process b) ∆H = – 63 kJ/mol ]

I get a) but how do I find b)?

Any help would be greatly appreciated!
Thanks in advance!
Title: Re: Find the enthalpy of neutralization, ∆H , in kJ/mol
Post by: cliverlong on September 28, 2009, 03:23:13 AM
Quote from: s3a on September 27, 2009, 11:29:06 PM
Answers:
[ a) q = – 3,132.35 = –3.1 x 103 J = –3.1 kJ, exothermic process b) ∆H = – 63 kJ/mol ]

I get a) but how do I find b)?

Any help would be greatly appreciated!
Thanks in advance!
Look at the units in the solutions

For part a) kJ

For part b) kJ/mol

So part b) tells you you need to convert the data you have, volumes and concentrations, into moles, then do your calculations.

Clive
Title: Re: Find the enthalpy of neutralization, ∆H , in kJ/mol
Post by: s3a on September 29, 2009, 02:40:41 PM
I get that part a) is kJ and that part b) is kJ/mol. What I don't get is how I am supposed to find how many moles of the solution there is since the final solution is a mixture of two different solutions (HCl and NaOH).
Title: Re: Find the enthalpy of neutralization, ∆H , in kJ/mol
Post by: sjb on September 29, 2009, 02:53:02 PM
How many moles of product do you get after reaction?
Title: Re: Find the enthalpy of neutralization, ∆H , in kJ/mol
Post by: s3a on September 29, 2009, 02:59:12 PM
How do I know what the chemical formula for the product is? (=my problem - I think)
Title: Re: Find the enthalpy of neutralization, ∆H , in kJ/mol
Post by: MrTeo on September 30, 2009, 12:47:05 AM
It's an acid - base reaction (a neutralization) so it's quite easy to understand what you get: a salt.

HA+BOH→BA+H2O