Specific heat capacity and final temperature

[moimoi24]

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,

please help me check what makes my answer wrong because the answer on the key is 97C...

Thanks a lot...

 

[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?

 

[ehild]

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

 

[moimoi24]

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]

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

 

[moimoi24]

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]

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