Question

A 35.0 kg block of copper metal melts at 1358 K. All of it melts to liquid at the same temperature (ΔHf = 2.67 × 10^4 J/kg). What is the change in entropy?

***Not sure at all! Thank you :)

Answer 1

@Michele_Laino :)

Answer 2

I think that the change in entropy is given by the subsequent computation:
\[\Large \Delta S = \frac{{\Delta H}}{T} = \frac{{2.67 \times {{10}^4}}}{{1358}} = ...?\]

Answer 3

ohh okay!

so then we get 19.661?

what are the units? :/

Answer 4

and would that be it? that's all that needs to be done to answer this problem? Or is there more? :O

Answer 5

that's right!

Answer 6

it is your answer!

Answer 7

oh yay!! i forget though, what units do i use for change in entropy?

Answer 8

it is a change of entropy in unit of mass of sample of copper, so the change in entropy of our sample of copper is:
\[\Large \Delta S = \frac{{\Delta H}}{T} = \frac{{2.67 \times {{10}^4}}}{{1358}} \times 35 = ...Joules/Kelvin\]

Answer 9

oh wait so 19.66 is not the answer? we have to still multiply by 35?

Answer 10

yes!

Answer 11

okay! so 19.66*35 = 688.1 J/K ? and 688 would be the final answer? that is the change in entropy?

Answer 12

yes! it is the change of entropy of our sample of copper

Answer 13

yay! and so now we are complete? :O

Answer 14

yes! our answer is complete!

Answer 15

yay!! thank you!! :D

Answer 16

thank you! :)