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April 25, 2015

Homework Help: Chemistry

Posted by Anonymous on Monday, November 15, 2010 at 7:40pm.

How much energy does it take to convert 0.800 kg ice at -20.C to steam at 250.C?

Specific heat capacities:
ice, 2.1 J g-1 C-1
liquid, 4.2 J g-1 C-1
steam, 2.0 J g-1 C-1

ΔHvap = 40.7 kJ/mol, ΔHfus = 6.02 kJ/mol

This is what I tried to do:
Heating ice
q= ( 2.1 J g-1 C-1)*(800g)*(20C)=...

Ice to water
q=(6.02 kJ / mol)*(800g)*(1 mol/18g)=...

Heating water
q=(4.2 J g-1 C-1)*(800g) * (20)
Is the change in temperature still 20? This is where I am confused...

Water to steam
q=(40.7 kJ/mol)*(800g)*(1 mol/ 18g)=...

Heating steam
q=(2.0 J g-1 C-1)*(800g)*(change in temp=???? 250-(-20)???)

Please can you check if I am doing this right and I need help with the change in temperature

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