Hi there, I have some serious problems with a couple of questions. Need help for exam revision.(adsbygoogle = window.adsbygoogle || []).push({});

1.1 The problem statement, all variables and given/known data

A 2kg chunck of ice at -10Celsius is added to 5kg of water at 45Celsius. What is the final temperature of the system?

1.2 Relevant equations

specific heat capacity of ice - 2100 Jkg^{-1}K^{-1}

specific heat capacity of water - 4190 Jkg^{-1}K^{-1}

latent heat of fusion for ice - 334 000 Jkg^{-1}

1.3 The attempt at a solution

Using formula E=mC(change in)T

E_{1}- 2 x 2100 x 10 = 42000J

E_{2}- 2 x 334 000 = 668 000J

E_{3}- 668 000 + 42 000 = 710 000J

E_{4}- 710 000=5 x 4190 x (change in)T T=33.89Celsius, so final temperature is 45-33.89=11.11, but the correct answer has to be 7.9Celsius.

2.1 The problem statement, all variables and given/known data

A cylinder with a piston contains 0.2 kg of water at 100 Celsius. What is the change in internal energy of the water when it is converted to steam at 100Celsius at a constant pressure of 10^{5}Nm^{-2}?

2.2 Relevant equations

latent heat of vaporisation of water - 2.26 x 10^{6}Jkg^{-1}

density of water - 1000 kgm^{-3}

density of steam - 0.6 kgm^{-3}

2.3 The attempt at a solution

Using (change in) U=(change in)Q - P x (change in)V

U=internal energy, Q=heat, P=pressure, V=volume

Change in heat is 2.26 x 10^{6}x 0.2 = 452 000 J

Can't manage more :(.

Supposed answer is 418.7 kJ.

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# Homework Help: What is the change in internal energy of the water

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