Use the following information on cr to determine the amounts of heat for the three heating steps required to convert 126.3 g of solid cr at 1760°c into liquid cr at 2060°c. mp = 1860°c bp = 2672°c enter in kj. useful data: \delta hδ hfus = 20.5 kj/mol; \delta hδ hvap = 339 kj/mol; c(solid) 44.8 j/g°c; c(liquid) = 0.94 j/g°c

Answer : The amount of heat required is, 639.3 KJ

Solution :

The conversions involved in this process are :

Now we have to calculate the enthalpy change.

where,

= enthalpy change or heat required = ?

m = mass of Cr = 126.3 g

= specific heat of solid Cr =

= specific heat of liquid Cr =

n = number of moles of Cr =

= enthalpy change for fusion = 20.5 KJ/mole = 20500 J/mole

Now put all the given values in the above expression, we get

    (1 KJ = 1000 J)

Therefore, the amount of heat required is, 639.3 KJ

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