Need Chem help! When 100. grams of aluminum at 100.degree C is added to 100. gra

Question

Need Chem help! When 100. grams of aluminum at 100.degree C is added to 100. grams of water at 25.0 degree C, the temperature of the water rises to 38.2 degree C. a) Why does the temperature of the aluminum go down by 61.8 degrees but the temperature of the water only goes up by 13.2 degrees? b) What is the experimentally determined specific heat capacity of aluminum? c) Use the specific heat capacity of aluminum determined in letter b to calculate the heat lost by aluminum when 100. grams of aluminum at 100.degree C is added to a cup of water at 25.0 degree C, the temperature of the water rises to 28.2 degree C. Use this information to determine what mass of water was in the cup.

Explanation / Answer

a)

because aluminium has less specific heat capacity, meaning, it requires less energy to decrease per unit mass, i.e. °C change is expected larger.

For water, it has a high Cp value, specific heat capacity, meaning that we require lots f heat removal to decrese its temperature

b)

Qaluminium = -Qwater

mal*Cal*(Tf-Tal) = -mw*Cw*(Tf-Tw)

substitute data

100*Cal*(38.2-100) = -100*4.184*(38.2-25)

Cal =  -100*4.184*(38.2-25) / (100(38.2-100)) = 0.89366 J/gC

c)

Heat lost when:

m = 100 g of al, T = 100°C, water = 25°C and dT = 28.2°C

so..

Qal = m*C*(Tf-Ti

Qal = 100*0.89366*(28.2-100)

Heat of aluminium lost -6416.478 J

mass of water

Qal = -Qwater

Qwater = m*C*(Tf-Ti)

6416.478 = m* 4.184*(28.2-25)

m = 6416.478 /( 4.184*(28.2-25)) = 479.242 g of water

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