1 a. The following information is given for water at 1atm: A 28.60 g sample of s
ID: 949783 • Letter: 1
Question
1 a. The following information is given for water at 1atm:
A 28.60 g sample of solid water is initially at -27.00 °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 20.00 °C.
b. The following information is given for magnesium at 1atm:
A 47.00 g sample of liquid magnesium at 703.0 °C is poured into a mold and allowed to cool to 28.0 °C. How many kJ of energy are released in this process. Report the answer as a positive number.
kJ
c. The standard enthalpy change for the following reaction is 903 kJ at 298 K.
What is the standard enthalpy change for this reaction at 298 K?
= kJ
d. The standard enthalpy change for the following reaction is -127 kJ at 298 K.
What is the standard enthalpy change for the reaction at 298 K?
= kJ
= kJ
= kJ
boiling point = 100.0 °C Hvap(100.0 °C) = 2.259×103 J/g melting point = 0.000 °C Hfus(0.000 °C) = 333.5 J/g specific heat solid = 2.100 J/g°C specific heat liquid = 4.184 J/g°CExplanation / Answer
1 a.
q absorbed = m*s*DT + n*DHfus + m*s*DT
= 28.6*2.1*(0+27)+28.6*333.5+28.6*4.18*(20-0)
= 13.55 kj
b.
q released = m*s*DT+m*DHfus+m*s*DT
= 47*1.017*(703-649)+47*368.3+47*1.339*(649-28)
= 58.972 kj
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