# Specific heat capacity and final temperature

## Homework Statement

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?

## Homework Equations

heat loss by the metal = heat gain by the water

## 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....

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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?

ehild
Homework Helper

## Homework Equations

heat loss by the metal = heat gain by the water

## The Attempt at a Solution

I solve it this way:
2800 g x 0.430 J/gC x (Tf-100) = 50 g x 4.2 J/gC x (Tf - 30)
Check the red one. Is it really the heat lost by the metal?

ehild

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

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

ehild
Homework Helper
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

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

ehild
Homework Helper
i think it should be100C - tf, since there is a decrease in temperature. my answer is 90C, is that correct?
Yes, you need to calculate with 100-Tf, but I got different result. Do not drop significant digits during the calculations.

ehild