Getting approximate final temperature from mixture of liquids of known temperature

[Herbsman.]

I remember, at college, mixing two seperate quantities of water, each of a different temperature, to get a final quantity of water that would be at roughly the temperature that I required.

For example, if I needed 1000ml of water at 25 degrees C, I would mix x amount of water from the hot tap which was known to be roughly 80 degrees C, and y amount of water from the cold tap which was known to be roughly 17 degrees C.

Is it actually possible to do this or am I imagining it?

Specifically, is there a formula that I can use to get a final temperature of roughly 80 degrees C by mixing x ml of water that is at roughly 100 degrees C and y ml of water that is at approximately 20 degrees C?

At what ratio would I need to mix x and y to achieve this?

 

[bi0boy]

Is it this easy?

100: 0 parts 20:4 parts 100
80: 1 parts 20:3 parts 100
60: 2 parts 20:2 parts 100
40: 3 parts 20:1 parts 100
20: 4 parts 20:0 parts 100

 

[Bob_the_lost]

Yes.

It is that simple. Add up the temps * volume then divide by the total volume. Done.

 

[Herbsman.]

I'll try that. Couldn't for the life of me remember WTF to do.

 

[MikeMcc]

Not necessarily - many of the naswers have depended on the desity of the solutions intoduced.

Look at the equation stoichio-metrically(?sp) and calculate the energy input and output. What's needed to change from one equilibrium condition to the other?

 

[Herbsman.]

Well I found an equation that used the specific heat capacity of water, but I couldn't work out how to rearrange it.

Stoichiometrically... there's a word I haven't heard for years!

 

[Hocus Eye.]

Herbsman

What are you up to? Is this a bit of home brewing or what?

 

[Herbsman.]

Just brewing coffee. I wanted to get the water to approximately 80 degrees without resorting to a thermometer, which would be taking it a bit too far, I think. I'll leave thatt sort of thing to the Quoad

 

[FaradayCaged]

I was going to post something similar since my boilers has packed in and can only run a bath by filling it with cold water then adding several kettles full of boiling water lol. Thanks .