Question

Calculate the change in internal energy of 2kg of water at 90 degree celcius when it is changed to 330m^3 of steam at 100oC. The whole process occurs at atmospheric pressure. The latent heat of vaporization of water is 226*10^6 J/kg

Answer 1

Just Remember two things
\[\large Q = Q \space ( H_2O _{(l->l)(90^o \to 100^o C)})+ Q \space(H_2O _{(l->g)(100^o \to 100^o C)})\]
\[\large Q \space ( H_2O _{(l->l)(90^o \to 100^o C)})= m*c_{water}*\Delta T\]
\[\large Q \space ( H_2O _{(l->g)(100^o \to 100^o C)})= m*L\]
m-->mass
L-->Latent heat
ΔT -->Change in temperature

Also to find mass of steam
mass = (density)(volume)

density of steam = 1000 kg/m^3

Now try :)

Answer 2

l-->liquid
g-->gas

Answer 3

@Prof.Grace , Any problem/doubt??

Answer 4

shouldn't the mass of water and steam be equal

Answer 5

I forgot to mention that c-->specific heat

Answer 6

c_water = 4.186 joule/gram °C

Answer 7

Be careful with units. :)

Answer 8

@Prof.Grace , There is something wrong with the question. The volume of steam is too high. Check the question again

Answer 9

that's exactly what i was wondering...but that's the question

Answer 10

I found a similar question on net.
See here
-> http://www.assignmentexpert.com/free-questions/question-on-physics-molecular-physics-and-thermodynamics-8650.html

Answer 11

Here Volume is 3.30 m^3

Answer 12

okay, i can see another version of the question - it says 3.3m^3

Answer 13

Q = (2*4.186*10) + (303.03*2.26*10^6)

Answer 14

= 83.72 + 684.85*10^6 = 6.5 * 10^8
please help me cross check it - it seems wrong to me

Answer 15

Q = (2*4.186*10)*10^3

Answer 16

684.85*10^6 -->100% wrong

Answer 17

wow that was very frank

Answer 18

Found the mistake
2.26 X 10^6 J/kg -->This is the right latent heat of ice
Your question has lot of decimal mistake
Also I think the mass should be 2 kg as you said

Answer 19

I got it. The water is partially converted to steam. I got it now.

Answer 20

Also density of steam is 0.6 kg/m3

Answer 21

Now find mass of steam from given volume

Answer 22

the answer should be 4.6 * 10^6

Answer 23

or 4.6 mJ

Answer 24

Exactly :D

Answer 25

nice job...***smiles***

Answer 26

Suggestion -->Your question had lot of decimal related errors which really made us troll this long

BTW, did you get the answer or you are telling me the final answer?

Answer 27

that was what i got

Answer 28

Very good. Keep these standard values in mind like density of water, steam and specific heat of water always. Many a time they won't be given in the question.

Good luck :D

Answer 29

kk

Answer 30

note:
mass of liquid is always=to mass of steam (that is if all liquid is evaporeted)
in same cases if not enough heat is given, onlt a fraction of liquid evaporate and then M(g)<M(l).

Answer 31

@mos1635 ,Thanks for clarifying. :)

Answer 32

always nice to see your work :)

Answer 33

:D .That's too sweet for my ears :D