Question

Question #ce902

Answer 1

You can't get the answer because your value of `ΔH` is incorrect.

Explanation:

The correct value of `ΔH` is -851.5 kJ.

Start with the balanced equation.

`"2Al(s)" + "Fe"_2"O"_3"(s)" → "2Fe(s)" + "Al"_2"O"_3"(s)"; ΔH = "–851.5 kJ"`

Step 1. Calculate the moles of `"Al"` used

`"Moles of Al" = 36 color(red)(cancel(color(black)("g Al"))) × "1 mol Al"/(26.98 color(red)(cancel(color(black)("g Al")))) = "1.33 mol Al"`

Step 2. Calculate the heat evolved

`"Heat evolved" = 1.33 color(red)(cancel(color(black)("mol Al"))) × "- 851.5 kJ"/(2 color(red)(cancel(color(black)("mol Al")))) = "-570 kJ"` (2 significant figures)