1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How to calculate the molar enthalpy

  1. Jan 19, 2009 #1
    1. The problem statement, all variables and given/known data

    1) add 60 ml of 1.0 mol/L Sodium Hydroxide solution to a polystyrene calorimeter.
    2) mix it with 40-ml sample of 1.0 mol/L sulfuric acid solution in a graduated cylinder.

    3) Add the acid to the base, stirring slowly with the thermometer. record the highest temperature recorded

    initial temp: 22.5
    highest: 26

    Cacluate the number of moles of the base (the limiting reagent)

    2) Calculate the change in molar enthalpy with respect to sodium hydroxide.
    2. Relevant equations

    3. The attempt at a solution
    I think, I solved it. n = c.v
    n = 0.06 * 1 = 0.06 mol NaOH

    2nd) H = m.c.t/n

    100g * 4.184 * 3.5 / 0.06
    = 24.4 KJ
    is this correct?

    the reason why I am confused is because the accepted value is 56kj/mol. My answers is way off. Wither I messed up during the experiment or in my writtten solution or in both
    Plz help
  2. jcsd
  3. Jan 20, 2009 #2


    User Avatar

    Staff: Mentor

    IMHO solution looks OK, so most likely there was something wrong with the experimental part.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook