You have a 0.75 kg block of gold. Gold melts at 1064°C. CAu = 130.0 J/kg g°C and △Hf for gold is 2.65 × 10^3 J/kg. Say you start at room temperature (22.0°C). How much heat must you transfer to melt all the gold?

Thank you!!!

Question

You have a 0.75 kg block of gold. Gold melts at 1064°C. CAu = 130.0 J/kg g°C and △Hf for gold is 2.65 × 10^3 J/kg. Say you start at room temperature (22.0°C). How much heat must you transfer to melt all the gold?

Thank you!!!

phi · Answer

you need some amount of heat to raise the temperature from 22 to 1064 (1042 deg increase)
and then some amount of heat to melt the gold once it reaches 1064

I assume one of your numbers is used to the first part and the other for the second part?

anonymous · Answer

i am not sure :/ i think so?

phi · Answer

probably  130 J  to raise 1 kg 1 degree

phi · Answer

so 130 J/kg-C * 0.75 kg*(1064-22)
for the first part.

anonymous · Answer

ohh and so we get 101595? :/

phi · Answer

and
2.65 × 10^3 J/kg *.75 kg
for the 2nd part

anonymous · Answer

so that gets 1987.5 ? 

and what happens from there? :O

also, what do you mean by 1st and 2nd parts? do we combine then somehow? :/

phi · Answer

yes, you add them

anonymous · Answer

ohh okay so i calculated the correct values?! 

and so 1987.5+101595 = 103582.5 ?

phi · Answer

looks good.  maybe write it in kJ:  about 103.6 kJ

anonymous · Answer

ohh okay!!! great!! thank you so much!! :D