Chemistry Phase Change HELP?

Posted on 2015-10-13 06:32:00 in Chemistry by MILLO

Please help

1.The following information is given for lead at 1atm:

boiling point = 1.740×103 °C Hvap(1.740×103 °C) = 858.2 J/g
melting point = 328.0 °C
Hfus(328.0 °C) = 23.00 J/g
specific heat solid = 0.1300 J/g°C
specific heat liquid = 0.1380 J/g°C

A 40.00 g sample of liquid lead at 580.0 °C is poured into a mold and allowed to cool to 23.0 °C. How many kJ of energy are released in this process?

2.
The following information is given for iron at 1atm:

boiling point = 2.750×103 °C
Hvap(2.750×103 °C) = 6.338×103 J/g
melting point = 1.535×103 °C
Hfus(1.535×103 °C) = 289.2 J/g
specific heat solid = 0.4520 J/g°C
specific heat liquid = 0.8240 J/g°C

A 47.40 g sample of solid iron is initially at 1.511×103 °C. If the sample is heated at constant pressure (P = 1 atm), _________?___________ kJ of heat are needed to raise the temperature of the sample to 1.796×103 °C.

Please help and thank you

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