Question

What will be the final temperature of a 655g sample of water, initially at 17.0oC, after 77.8 kJ have been added to it?

Answer 1

@CShrix

Answer 2

Use formula of specific heat capacity\[E=m*c*(T _{f}-T _{i})\]
\[77800=0.655*4.18*(T _{f}-17)\]
Find Tf.

Answer 3

lol "tf"

Answer 4

77800=-46.5443Tf

Answer 5

@LeibyStrauss Tf=-1671.525837

Answer 6

It doesn't look right. The initial T was 17 degree celsius. If heat was added you won't have a negative number.

How did you get -46.5443Tf

If you use the formula written by Hoslos you need to distribute 655∗4.18 to Tf as well as to 17

As a correction q = m*c*(Tfinal - T initial) mass is 655 not 0.655

Do you have the formula q = m*c*(Tfinal - T initial) or do you have a similar formula?

If you have the same one how can you re-write (Tfinal - Tinitial)?

Answer 7

I do not.

Answer 8

What formula do you have for q?

q = heat

Answer 9

No formulas were given on the sheet.

Answer 10

q = mass * specific heat capacity * change in temperature

There are different ways of writing the formula, one way is

\[q = m \times c \Delta T\]

q = heat

m = mass in grams

c = specific heat capacity J/gK

Delta T = T final - T initial in Kelvin

Can you plug in the values in to the formula?

Answer 11

So I need to change the 17.0 oC to K?

Answer 12

No. Since it is change of T. Meaning, if something changes from 10 degrees Celsius to 25 degrees celsius, the change in T is 15 degrees Celsius. If we convert it to K it is 288.15K - 283.15K which is 15 K. So we have the same change whether it is C or K.

Answer 13

I'm getting confused

Answer 14

For now just plug in the values you have into the formula. We can come back later to your question regarding converting to K. For now, you can solve the problem as if the units of the formula are in C

Answer 15

655g * 77.8* 17.0oC

Answer 16

Is that it basically?

Answer 17

q = m*c*deltaT

The units on q is J

Your question has 77.8 kJ

Answer 18

@staldk3 , I made a slim mistake on my workout. Instead of converting the mass to kg, it should remain as g. Hence being:\[\frac{ 77800 }{ 655*4.18 }=T _{f}-17\]\[\frac{ 77800 }{ 655*4.18 }+17=45.4 C\]

Answer 19

Tf= 45.4 Degrees.

Answer 20

So the kJ has to be converted to J which makes it 77800 J?

Answer 21

Correct

Answer 22

Finally got the right answer.

Answer 23

Are you done?

Answer 24

And we need 3 sig figs instead of 2?

Answer 25

Correct.

Answer 26

Why is that? What about the +17?

Answer 27

The original question had how many sig figs?

Answer 28

Oh okay so you just left out the .0 part?

Answer 29

17.0 is 3 sig figs

Answer 30

Right. But in the equation it was left as 17. Why I thought there should be 2 sig figs.

Answer 31

I did not post the equation. If you want to work it through step by step, I can help you, but you need to plug the values in.

Answer 32

I did it on a calculator and got the same answer. I'm good on it. Just got mixed up on the 17 part for a bit but I think they just left off the .0 on the 17.0 just to type it easier. It's all good.

Answer 33

Ok.

Answer 34

Thanks

Answer 35

You're welcome