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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: sharbeldam on January 17, 2021, 02:13:50 AM

Title: Question about enthalpy of dissolution
Post by: sharbeldam on January 17, 2021, 02:13:50 AM

I'm asking this because I watched 3 youtube videos and each one explained it differently with different results

when we have let's say 50 grams of NaOH dissolved in 100g water and the temperature of the water increases by 17.5, and we are given that the heat capacity of water is 4.18 and we are required to find the enthalpy of dissolution

when we use deltaH=mC(deltaT)
in the m, do we use the total mass of solution or only the mass of water?
m=100 or 150? that makes a lot of difference!
one video used 100 and then only used the mass of NaOH to get the moles and then find the molar enthalpy, the other videos used 150 from the start as m...

any clear answer please?

thanks

Title: Re: Question about enthalpy of dissolution
Post by: AWK on January 17, 2021, 03:28:19 AM

NaOH also has a specific heat capacity.

Title: Re: Question about enthalpy of dissolution
Post by: Borek on January 17, 2021, 05:16:21 AM

Technically you should use 150g of solution and heat capacity of 33.3% solution, every other approach is just an approximation.

150g and heat capacity of water is probably the closest you can get without consulting detailed tables.