Question #a9795

1 Answer
Oct 26, 2016


#"10.43 kJ"#


Notice that the problem provides you with the molar enthalpy of fusion of hydrogen bromide, which essentially tells you how much heat is required to melt one mole of solid hydrogen bromide at its melting point.

In this case, you know that every mole of hydrogen bromide that undergoes a solid #-># liquid phase change requires #"2.41 kJ"# of heat.

The first thing to do here will be to convert the mass of hydrogen bromide to moles by using the compound's molar mass.

#350.2 color(red)(cancel(color(black)("g"))) * "1 mole HBr"/(80.912color(red)(cancel(color(black)("g")))) = "4.3282 moles HBr"#

Now you can use the molar enthalpy of fusion as a conversion factor to find the heat needed to melt your sample

#4.3282 color(red)(cancel(color(black)("moles HBr"))) * "2.41 kJ"/(1color(red)(cancel(color(black)("mole HBr")))) = color(green)(bar(ul(|color(white)(a/a)color(black)("10.43 kJ")color(white)(a/a)|)))#

I'll leave the answer rounded to four sig figs.