gen chem question!!! helppp

[JustwantDDS]

How many calories are needed to convert 8g ice at -23C to water at 52C?

sp heat water/ice 1 cal/g C
Hfusion water 80 cal/g

ok so i set it up like this

q1= mcAt= (8)(1)(23)=184
q2= nHf= (0.44mol)(80)=35.5
q3=mcAt=(8)(1)(52)= 416

q1+q2+q3= 635.5

answer is (75)(8)+(80)(8)

and in the explanation they do q2= mHf m for mass
i thought it was phase change=q=MOL * Hf

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[AlbinoPolarBear]

How many calories are needed to convert 8g ice at -23C to water at 52C?

sp heat water/ice 1 cal/g C
Hfusion water 80 cal/g

ok so i set it up like this

q1= mcAt= (8)(1)(23)=184
q2= nHf= (0.44mol)(80)=35.5
q3=mcAt=(8)(1)(52)= 416

q1+q2+q3= 635.5

answer is (75)(8)+(80)(8)

and in the explanation they do q2= mHf m for mass
i thought it was phase change=q=MOL * Hf

Hfusion water 80 cal/g

You want the final answer to be in cal, so you gotta cancel out the g by using the mass.

 

[MAdental]

Always look at UNITS. what did they give u in the question. Cal/g is given, there is no way u can use Moles

 

[herkulease]

Its usually mass not moles.

the way you do it. mols and Grams never cancel out for q2.

you would get 80 mols X cal/Grams.

the safest thing to convert to what is given if you have to. don't go off your memory.

if you were given calories per kilograms convert your sample into kilograms if your sample isn't kilograms.

If your sample is already kilograms then obviously do not convert it.

 

[JustwantDDS]

Hfusion water 80 cal/g

You want the final answer to be in cal, so you gotta cancel out the g by using the mass.

sighhhh trueee
ugh brain fried.