# Specific heat capacity and final temperature

1. Sep 23, 2012

### moimoi24

1. The problem statement, all variables and given/known data

A 2.8 kg sample of a metal with a specific heat of 0.43KJ/KgC is heated to 100.0C then placed in a 50.0 g sample of water at 30.0C.* What is the final temperature of the metal and the water?

2. Relevant equations

heat loss by the metal = heat gain by the water

3. The attempt at a solution

I solve it this way:
2800 g x 430 J/gC x (Tf-100) = 50 g x 4.2 J/gC x (Tf - 30)

my final answer is 100 C,

Thanks a lot....

2. Sep 23, 2012

### moimoi24

i solve it again and i got 114 as the answer because of 0.43KJ/KgC, it will be 0.43J/gC... Please help me with this one, what makes it wrong?

3. Sep 23, 2012

### ehild

Check the red one. Is it really the heat lost by the metal?

ehild

4. Sep 23, 2012

### moimoi24

is it 2800 g x 0.43J/gC x 70 C?

5. Sep 23, 2012

### ehild

You said that the heat lost by the metal is equal to the heat gained by water.
The metal cools down from 100 C° to Tf, how much heat releases in the cooling process?

ehild

6. Sep 23, 2012

### moimoi24

i think it should be100C - tf, since there is a decrease in temperature. my answer is 90C, is that correct?

7. Sep 23, 2012

### ehild

Yes, you need to calculate with 100-Tf, but I got different result. Do not drop significant digits during the calculations.

ehild