Question

Liquid sodium is being considered as an engine coolant. How many grams of liquid sodium (minimum) are needed to absorb 1.00 MJ of energy (in the form of heat) if the temperature of the sodium is not to increase by more than 10.0 °C? Use CP = 30.8 J/(K·mol) for Na(l) at 500 K.

Answer 1

@zbay

Answer 2

So what formula do you think we should use here?

Answer 3

the heat formula?

Answer 4

q=m x c x delta T ?

Answer 5

seems to me that one should work I would plug in the numbers insuring the units cancel and solf for m

Answer 6

i tried to plugged it in but im trying to figure out which one is the initial and which is final, cuz to find delta T you gotta take Final - Initial

Answer 7

just use 10 C as delta t

Answer 8

oh, so what about that 500 K ?

Answer 9

283 k

Answer 10

wait

Answer 11

ok use 283 kalvin the 500k is for the C of sodium at 500k

Answer 12

wait what? im lost -.-

Answer 13

so i set up the equation like this:
1.00x10^6 = (m)(30.8)(10) <--- is that right?

Answer 14

change the 10c to 283k so you go from celcius to kalvin and your units will cancel. I always put the units in so you can make sure they cancel out and you got the answer you are really looking for. you will also have to get your megajoule and joules into the same unit

Answer 15

Look at your specific heat and get all your other units to match that one

Answer 16

so this heat equation measured in Kelvin instead of Celcius ?

Answer 17

so i think it's 1x10^12 = (m)(30.8)(283) <--- it should be alright so solve now

Answer 18

your specific heat given is measured in Kelvin and not celcius so

Answer 19

i got such a big number for mass, I'm not even sure if its correct....it's 114726263.1

Answer 20

alright 1mj is 1x10^6 j and this will leave you in moles so you have to convert that to grams

Answer 21

wait a minute, i clicked on the "Hint" and it show me this: "A temperature change, ΔT, has the same value in kelvins as it does in degrees Celsius. Thus, ΔT = 10.0 °C = 10.0 K. "

Answer 22

so it's not 283 but 10 ? o_0

Answer 23

no q=1,000,000 jolues

Answer 24

yes, so you change 1x10^6 MJ to J = 1x10^12

Answer 25

no the system needs to absorb 1 mj and 1 mj = 1x10^6 j

Answer 26

ohh i see

Answer 27

can you please put the whole equation together, so i can see better cuz im really confused on which number to put... @.@

Answer 28

\[1x10^6 j = m (30.8\frac{j}{k*mol})(283.15k)\]

Answer 29

notice that the kelvins cancell right off the bat and you are left with j/mol

Answer 30

how to get the mol?

Answer 31

so after you solve for m what unit is your answer in?

Answer 32

what do you mean how do you get the mol?

Answer 33

unit should be in gram

Answer 34

you don't know how to convert from moles to grams?

Answer 35

do you have to in this case?

Answer 36

yes if they want the answer in grams you must convert

Answer 37

\[114.67 mol Na (\frac{22.99 g Na}{1 mol Na})=342.9 g Na\]

Answer 38

it's wrong...

Answer 39

i think the delta T in this case is 10 and not 283

Answer 40

and if i use that then i would get 3246 mol of Na

Answer 41

then to grams so...74350 g <-----big number o_0

Answer 42

\[114.67 mol Na(\frac{22.99 g Na}{1 mol Na})=2636.26 g Na\]

Answer 43

i messed up on the conversion

Answer 44

hmm still wrong..

Answer 45

it sait (Delta T) in K equals to Celcius...do not add 273

Answer 46

it said*

Answer 47

my answer was correct.. 74350 g lol =.=

Answer 48

alright