Thermochemistry

Question

I'm not sure what I need to do here...

 

If 25.0 g of ethanol at 5.0 °C is mixed with 50.0g of ethanol at 75.0 °C, what with the final temperature of ethanol be, assuming no heat is lost to the surroundings?

Answer 1

Hi Trenda,

 

As the two amounts of ethanol mix, energy is transferred from one to the other as heat, until an equilibrium temperature T is reached.

 

The formula for this heat transfer is

Q = mcΔT

 

Q is the heat, m is the mass, c is the specific heat of the material, and ΔT is the change in temperature.

 

Q = 25.0g * c * (T - 5.0 °C) = 50.0g * c * (75.0 °C - T)

 

Normally you'd need to know c, but since both are the same material, these cancel

 

25(T-5) = 50(75-T)

 

You can solve this fairly easily now for the final temperature T.