how do I do this?

[Shawn]

When 165mL of water at 22C is mixed with 85mL of water at 82C, what is the final temperature? (Assume that no heat is lost to the surroundings; d of water is 1.00g/mL)

 

[njmodi]

HINT: Related to the specific heat capacity of water

 

[StevenMara]

I don't know, but I am guessing the answer 33C.

 

[Savij]

42.4C...it's basically an average
165*22+85*82/(165+85)

 

[Savij]

Originally posted by: njmodi
HINT: Related to the specific heat capacity of water

Why does that even come up in this problem? We're dealing with nothing but water, right?

 

[njmodi]

Originally posted by: Savij

Originally posted by: njmodi
HINT: Related to the specific heat capacity of water

Why does that even come up in this problem? We're dealing with nothing but water, right?

You are right.. the heat capacity would have cancelled out since both substances are water - I was making it more complicated than needed 🙂

 

[Shawn]

how would I do it if the heat capacities were different?

 

[Savij]

Originally posted by: Shawn
how would I do it if the heat capacities were different?

I can't remember, but here's a bump for you.

 

[Lonyo]

Originally posted by: Shawn
how would I do it if the heat capacities were different?

Possibly work out how many joules of energy each of the two things has, then work out the average heat capacity of the two substances combined and go from there maybe?

 

[Savij]

what are the units for heat capacity?

 

[Caesar]

Originally posted by: Savij
42.4C...it's basically an average
165*22+85*82/(165+85)

WINNAR. Its a simple mixing problem of complete heat load.

Edit: Coming from the guy who is an environmental engineer dealing with thermal plume permitting for power plants.

 

[Savij]

Originally posted by: CaesaR

Originally posted by: Savij
42.4C...it's basically an average
165*22+85*82/(165+85)

WINNAR. Its a simple mixing problem of complete heat load.

Edit: Coming from the guy who is an environmental engineer dealing with thermal plume permitting for power plants.

Then you can help with his second question.

how would I do it if the heat capacities were different?

 

[simms]

Originally posted by: Savij
what are the units for heat capacity?

KJ/mol K?

 

[Fenixgoon]

Originally posted by: Savij
42.4C...it's basically an average
165*22+85*82/(165+85)

the amounts of water differ though, so its not necessarily going to be an average

 

[Savij]

Originally posted by: Fenixgoon

Originally posted by: Savij
42.4C...it's basically an average
165*22+85*82/(165+85)

the amounts of water differ though, so its not necessarily going to be an average

(22+22+22+22+22+22+22+22+22...+22+82+82+82+82+82...+82)/total number of mL

looks like an average to me.