# Chemistry question - moles and thermochemistry

#### jobberd

##### Banned
0.24 grams of a magnesium ribbon were placed in 50 ml of aqueous HCl. the initial temperature was 20 Celsius, while the final temperature was 42 Celsius. According to the teacher, all calculations must be done with the density (1 ml = 1 g) and specific heat capacity (4.18) of water, and not HCl. how are you supposed to find out the quantity of heat (q) in joules transferred?
ive been working on this forever, and i can't get it :/ please help, if you can!

#### SWirth86

##### Golden Member
Ouch.... Chemistry really sucks.
I would bust out my book from last year and help you, but I'm too lazy

If you don't get it after a little while I'll try and help you some.

#### notfred

##### Lifer
my pet mole failed thermochemistry.

#### jobberd

##### Banned
Any links would help too. all i need to know is how to determine the quantity of heat transferred in a reaction, when mass of reactants and temperature change is known

#### Wheatmaster

##### Diamond Member
btw mole day was June 22

#### minendo

##### Elite Member
Do you know the actual answer? As in, is it in the back of the book?

(4598J)

#### GoSharks

##### Diamond Member
Q=(grams)(specific heat)(delta temperature)

q=50*4.18*22
q=4598

#### Bobomatic

##### Senior member
btw mole day was June 22
no, it was october 23. My chem teacher said they have fireworks or something at 6:02 am. (6.02x10^23)

Q=(grams)(specific heat)(delta temperature)

q=50*4.18*22
q=4598

how are you getting the grams to be 50? shouldnt you write out the reaction mg+HCl+H2O arrow mgcl... and getting the moles of mg and get the grams of the water at the end of the reaction and use those grams for the m in q=mct?

#### jobberd

##### Banned
how are you getting the grams to be 50? shoudnt you add the .24 grams of magnesium or something? shouldnt you write out the reaction mg+HCl+H2O arrow mgcl... and getting the moles of mg and get the grams of the water at the end of the reaction and use those grams for the m in q=mct?
You're right, thanks a bunch! and thanks to the rest of you too, you were all a big help

#### GoSharks

##### Diamond Member
Originally posted by: Bobomatic
how are you getting the grams to be 50?

thats how we did it a few weeks ago for my ap chem class. the thing being heated is the 50ml/g of water, not the Mg. we did not do anything with the moles of anything the way we did it (until we found the J/mol)

#### fluxquantum

##### Platinum Member
you're welcome. glad we could help.