Calorimeterquestion

Question

a 25.0 g sample of zinc is heated, then placed in a calorimeter containing 65.0 g of water. Temperature of water increases from 20.00 C to 22.50 C. The initial temp. of the zinc was 92.23 C. What is the specific heat of the zinc? (Final temp of zinc and water are the same)

Answer 1

THe key concept to understand with this question is that the heat LOST by the zinc when it cools has to equal the heat GAINED by the water as it rises in temperature from 20 to 22.50.

SO heat lost by zinc is governed by the equation:

q= -mcdeltaT

q = -(25.0) c (22.50-92.23)

and the heat GAINED by the water is:

q= +mcdeltaT

q = (65.0 g ) (4.18 J/gramC ) (22.5 - 20)

set these two equations equal to each other and solve for c!

-(25.0) c (22.50-92.23) = (65.0 g ) (4.18 J/gramC ) (22.5 - 20)

1743 c = 679

c = 0.390 J/gC

Notice the negative sign for the "heat lost"; positive sign is for "heat gained". There is no such thing as a negative heat capacity.