Question

An 8.5g Ice Cube is placed into 255g water.
Calculate temperature change in water upon the complete melting of the ice. (Assume all the energy required to melt the ice comes from the water. )

Answer 1

okay for this you have to use this equation "q=m*C*\(\Delta T\)",
and, q=\(\Delta H_{fusion}*n\). remember that this last one can be n or m, depending on what the units for \(\Delta H_{fusion}\) are.

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Also, remember that \(\Delta T=T_f-T_i\)

where, \(T_f\)=final temperature and \(T_i\)=initial temperature

although this won't be used for this specific question
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So, what you wanna do is to determine what you're ultimately looking for.
The question asks for "Calculate temperature change in water", which is \(\Delta T\).

So, first you have to find the heat (q) required to melt the ice (which will come from the water).

so convert the mass of ice to grams, then mass to moles.
(look up a conversion chart on google if that helps).

and use \(q_{ice}=\Delta H_{fusion}*n\)

(\(\Delta H_{fusion}\) needs to be looked up)

Then, since all the heat to melt the ice came from the water, we express it mathematically, like this: \(q_{ice}=-q_{water}\)

so, \(q_{ice}=-q_{water}=m*C*\Delta T\)

Here you're using the heat capacity (C) for water, the mass of the water (not including the ice) and you're solving for \(\Delta T\).

Answer 2

EDIT: sorry i had a mental relapse when i said "convert the mass of ice to grams, then mass to moles." It should only be "mass to moles".

Answer 3

haha okay im almost done reading what you put.

Answer 4

okay.

Answer 5

okay im on the first step let me look in the book or heat required to melt the ice unless its 40.7 kj/mol

Answer 6

no thats to vaporize (turn into steam).

Answer 7

okay so.. in the book to melt a solid ice cube to water is....2) Ice melting to liquid = 6.02 kJ/mol

Answer 8

okay, so convert the mass of ice to moles

Answer 9

so i could do the 6.02 kj/mol // 1000 kj= .00602 mol

Answer 10

right?

Answer 11

Just follow what i said

Answer 12

n=m/M= 8.5 g /18g/mol =

Answer 13

what does the q mean again?

Answer 14

heat

Answer 15

okay .472 moles

Answer 16

okay, not find the heat required to melt that much ice

q=\(\Delta H_{vap}*n\)

Answer 17

now find*

Answer 18

okay ... .472mol (6.02 kj/ 1 mol)=2.84

Answer 19

good stuff! don't forget the units 2.84 kJ

now, the heat required to melt the ice comes from the water, so,

\(q_{ice}=- \;q_{water}\)

2.84 kJ = -2.84 kJ

use the second formula,

-2.84 kJ = m*C*\(\Delta T\)

you should convert 2.84 kJ to J (multiply by 1000).

Answer 20

-2840J

Answer 21

nice, now solve for \(\Delta T\),

-2840 J = m*C* \(\Delta T\)

C=4.184 J/\(C^{\circ}g\)

Answer 22

okay @aaronq
i got -5608.56 moles

Answer 23

your answer should be in terms of degrees celsius because you're solving for the change in temperature, not moles.

Answer 24

so you have 255 g of water

-2840 J = (255 g)*(4.184 J/C*g)*\(\Delta T\)

Answer 25

sorry, celcius

Answer 26

hey @aaronq I have to go. I will continue this tomorrow. Have a goodnite!

Answer 27

okay, see ya !

Answer 28

Hi @aaronq Sorry I had go go, my folks got back home, and I didnt want them to see me crying.

Answer 29

Im ready, refreshed and Im ready to go :)

Answer 30

So did you get that last part?

Answer 31

yes i did :) it is wait haha

Answer 32

(-2840 J) = (255g)(4.184 J/ C*g) (delta T)

I rearranged to get the delta T(temperature change) to one side so it looks like this, right?
\[\Delta T = -2840 J (255g)(4.184\frac{ J }{ C*g }\]

Answer 33

not quite, you're algebraically solving.

A*B=C ->solving for A, A=\(\dfrac{C}{B}\)

right?

Answer 34

yes, okay so then it would look like this, hold on

Answer 35

\[-2840 J / (255 g) (4.184 \frac{ J }{ C * g } )\]

Answer 36

thats' right. notice that the units "g" and "J" will cancel out.

Answer 37

okay they cancel

Answer 38

i got then

Answer 39

-2.66 Celcius

Answer 40

okay good stuff.

Answer 41

is this correct? then Im guessing we have to do another calculation, right? @aaronq

Answer 42

no that's it, the question is asking you for the change in temperature.

The change in temperature will be -2.66 celsius, since you're not given the temp of the water, you can't say what it's final temp will be.

Answer 43

oh thats true..................... YOURE SO AWESOME! :D

Answer 44

haha thanks ! chemistry is my strong point

Answer 45

it really is haha okay, I have another Problem, I will close this one. thank you very mucH!

Answer 46

no problem! okay

Answer 47

when I try messaging you it says only accepts people that are fanned, what does that mean? I was thinking about sending you a message if and when I need help later on.

Answer 48

@aaronq

Answer 49

yeah, sorry about that. I switched my settings so only people i'm a fan of will be able to msg me because i used to get A LOT of messages of people asking for help, it got pretty annoying. But i've fanned you, now you can msg me! lol

Answer 50

okay, thank you, i was like WHA?! 0.o haha

Answer 51

WAIT!!! i just saw the rest of the quesiton to the problem haha

we found the temperature change.
it says
calculate temperature change in water upon the complete melthing of the ice. Assume all the energy required to melt the ice comes from the water. So then that -2.66 C is still the answer right? I just want to double chekc.

Answer 52

yep, we calculated the heat needed to melt the ice, which would be extracted from the liquid water, and we found the change of temperature of the water.

Answer 53

okay, haha I was gonna freak when I saw that i was like wait aminute did i forget something haha.

Answer 54

thank you Aaronq. Im going to close this problem, i have to clean up the house to give myself a quick break.

Answer 55

okay! clearing up your head with some other activity is a good idea, see ya

Answer 56

thank you Aaronq. Im going to close this problem, i have to clean up the house to give myself a quick break.