Question

Calculate the enthalpy when 850.0g of ice melts ΔH_fusion for ice=6009.5 J/mol?

I'm not really sure what ΔH_fusion means and how to use that to solve the problem?

Answer 1

`DeltaH_"fus"`, the enthalpy of fusion, is the heat flow input at constant atmospheric pressure (i.e. lab bench conditions) required to melt some mass of solid into a liquid. Therefore, it is positive (why?).

And so, since `DeltaH_"fus" = "6009.5 J/mol"`, we'll need the ice mass in mols.

`850.0 cancel"g ice" xx ("1 mol")/(18.015 cancel"g water") = "47.18 mol ice"`

Therefore,

`color(blue)(DeltaH_"fus") = 47.18 cancel"mol ice" xx "6009.5 J"/cancel"mol ice"`

`= 2.835 xx 10^5 "J" = color(blue)("283.5 kJ")`