Need serious help with these enthalpy of neutralisation calculations

  • Thread starter jackal22
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  • #1
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ok i keep reading that ideally they (neutralisation enthalpies) are meant to be around 58KJ

here is my problem:

im reacting 50cm3 of NaOH with 25cm3 of HCl

the HCl is 1 mole NaOH is also 1 mole.

my moles calculation is: (1x25)/1000 which gives me 0.025

the i do :

((mass x specific heat x change in temp)/moles)/1000

i get -25.4 which is no where near 58 ish...

same thing when i use nitric acid instead, i end up with 27.08. However when i use sulphuric acid i get a result of 52.416 (sulphuric acid is 0.5 molar)

so my question is, am i getting something wrong? im using the mass of the substance needed to neutralise the acid for mass (reading it off a graph) & im using 4.2 for specific heat

also is there any reason for why some are better at neutralising is it like to do with more H+ ions ?

i would really appreciate any help
 

Answers and Replies

  • #2
GCT
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Neutralization enthalpies are based on the net ionic equation for water

H+ (aq) + OH- (aq) ----> H2O (l)

that's why the enthalpies are fairly the same. The slight differences may pertain to the hydration interactions of the respective components (for instance, Na + and Cl-) with water.
 
  • #3
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thanks, =)
 

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