Question #38eda

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Answer 1 · 2017-02-21T22:31:09

#sf(7.9)#

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")#