Question #38eda

1 Answer
Feb 21, 2017

sf(7.9)

Explanation:

Use the idea that the heat given out by the aluminium = the heat taken in by the water.

I notice that the heat capacities are given per mole so we need to work out the number of moles of aluminium.

I will use sf(A_r[Al]=27)

:.sf(n_(Al)=m/A_r=60/27=2.22color(white)(x)"mol")

The heat given out by the aluminium =sf(n_(Al)xxC_(Al)xxDeltaT)

sf(DeltaT=75-20=55color(white)(x)"deg")

:.Heat given out = sf(2.22xx24.3xx55=2967color(white)(x)J)

This heat is taken in by the water.

:.sf(2967=n_(H_2O)xxC_(H_2O)xxDeltaT)

In this case sf(DeltaT=20-15=5color(white)(x)"deg")

:.sf(2967=n_(H_2O)xx75.3xx5)

:.sf(n_(H_2O)=(2967)/(75.3xx5)=7.88color(white)(x)"mol")