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Chemistry Question

can anyone help with these two..

A 0.1375g sample of solid magnesium is burned in a constant volume bomb calorimeter that has a heat capacity of 1769 J/degrees C. The calorimeter contains exactly 300g of water, and the temperature increases by 1.126 degrees C. Calculate the heat given off by burning Mg, and give your answer in both kJ/g and in kJ/mol.


and

Calculate the work done in joules when 1.0 mole of water is frozen at 0 degrees Celcius and 1.0 atm. The volumes of one mole of water and ice at 0 degrees celcius are 0.0180 L and 0.0196 L respectively.
Reply 1
Avatar for Tednol
Tednol
10
Jennym0183
A 0.1375g sample of solid magnesium is burned in a constant volume bomb calorimeter that has a heat capacity of 1769 J/degrees C. The calorimeter contains exactly 300g of water, and the temperature increases by 1.126 degrees C. Calculate the heat given off by burning Mg, and give your answer in both kJ/g and in kJ/mol.


Can't help you but... welcome to UK Learning. Sure you'll get an answer from someone more useful than myself!
Reply 2
Avatar for phillip04
phillip04
Jennym0183
can anyone help with these two..

A 0.1375g sample of solid magnesium is burned in a constant volume bomb calorimeter that has a heat capacity of 1769 J/degrees C. The calorimeter contains exactly 300g of water, and the temperature increases by 1.126 degrees C. Calculate the heat given off by burning Mg, and give your answer in both kJ/g and in kJ/mol.


and

Calculate the work done in joules when 1.0 mole of water is frozen at 0 degrees Celcius and 1.0 atm. The volumes of one mole of water and ice at 0 degrees celcius are 0.0180 L and 0.0196 L respectively.



Not done this for a long time so am not 100% sure, maybe some1 can check if this is right..

a) heat given off = mass x specific heat capacity x change in temp

= 300.1375 x 1769 x 1.126 = 597,842j/g = 597.8 kj/g

to find kj/mol, divide the answer above by number of moles of Mg (mass/formula mass) = 0.1375/24.3 = 5.6x10^3

597.8/5.6x10^-3 = 106,758 kj/mol

dont know second bit.
Reply 3
Avatar for innitman_uk
innitman_uk
Jennym0183
can anyone help with these two..

A 0.1375g sample of solid magnesium is burned in a constant volume bomb calorimeter that has a heat capacity of 1769 J/degrees C. The calorimeter contains exactly 300g of water, and the temperature increases by 1.126 degrees C. Calculate the heat given off by burning Mg, and give your answer in both kJ/g and in kJ/mol.


and

Calculate the work done in joules when 1.0 mole of water is frozen at 0 degrees Celcius and 1.0 atm. The volumes of one mole of water and ice at 0 degrees celcius are 0.0180 L and 0.0196 L respectively.


hmm

since work done=energy transferred, for this second part, maybe you could use this:

energy transferred = mass x latent heat of fusion for water (334 kJ per kg)

you can get the mass from :

mass=volume (of water) * density (of water)

hope this helps :wink:

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