Yr 11 Chemistry... help!!!!!

[Olivia L]

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Hey guys... I need serious help.
Question: explain and evaluate how water's ability to absorb heat is used to measure energy changes in chemical reactions. I need to design a first-hand experiment to measure the change in temperature when substances dissolve in water and describe how you calculate the molar heat of soloution.

Any ideas...?

[amied92]

Umm not sure about the molar heat of the solution but cant you get a bunch of tap water at the same temp, dissolve substances in different containers and record temperature differences?

umm then describe your obsevations... i would have to look up how to calculate molar heat.. i know how to calculate molar mass :S

hope that helps... feel free to ask and questions and im sure we can figure something out.

[Olivia L]

thanks so much! I'll give it a go

[shady145]

u'll probably have to use (delta)H=-mc(delta)t
have u come across this eq yet?
with the molar heat of solution, when ur testing different substances measure the mass u use. eg. if u use salt solution, then weigh the amount of salt u put in. this will allow u to work out moles.
so
1. put 100ml water in beaker, record start temp (distilled water, so dnt get it out of the tap like aimed92 said) heat for 10 minutes or so using a bunsen burner. record the max temperature reached in the time, also record the temp every minute.
2. add say 10g of salt to 100ml distilled water, record start temp, heat for 10 minutes and record temp every minute.
3. use the equation (delta)H=-mc(delta)t to work out (delta)H for both steps 1&2, which is the heat energy.
4. calculate the amount of moles of salt used. u c how to finish it? if not ask me

[zazzy1234]

Originally Posted by Olivia L

Hey guys... I need serious help.
Question: explain and evaluate how water's ability to absorb heat is used to measure energy changes in chemical reactions. I need to design a first-hand experiment to measure the change in temperature when substances dissolve in water and describe how you calculate the molar heat of soloution.

Any ideas...?

here is an experiment we did in yr 12, not sure if it helps though but here is goes:

1. Find the mass of fuel burnt by weighting the fuel and the container befoe and after heating.
2. Find the number of fuel burnt
3. From the rise in water temp calculate the fuel produced by combustion of that many moles of fuel burnt using (delta)H=-m(delta)T
4. caluate how could've been produced by the combustion of 1 mole of fuel.

[Ishynooshy]

zazzy1234: The OP needs an experiment where something needs to be dissolved in water, not heated by a fuel.

Olivia, this is what I would do:
1. Measure out 100mL of distilled water and pour into foam cup that is in another foam cup.
2. Use thermometer and get initial temp record.
3. Measure out 5.0g of NaOH and dissolve it in the water
4. Record final temp
5. Repeat with 5.2g NH4Cl

What you should get is a temperateure increase with the NaOH and decrease with the NH4Cl.
If you need help with the calculations give a shout .

[maplestory]

Originally Posted by Olivia L

Hey guys... I need serious help.
Question: explain and evaluate how water's ability to absorb heat is used to measure energy changes in chemical reactions. I need to design a first-hand experiment to measure the change in temperature when substances dissolve in water and describe how you calculate the molar heat of soloution.

Any ideas...?

heyy!
i m working on this assignment too!

u have to use the delta thingy equation, rite?

when's urs due?

i have to work out that prac this wed & it's due onli on the 3rd of aug

it seems eazy yet it;s hard , isn't?

[Olivia L]

Thanks everybody!!

it was due in a week or so ago... we got two weeks to do it

now ive got to write a speech about it in the holidays... ???!?!?!? I dont quite know what the speech has to be on but oh well...

[melon13]

hey, Ive got the same assinment.
the posts have helped alot, but are there any other chemicals that will usefull. just to broaden it?
anyway let me know. ta