# Homework Help: Find the mass of ethyl alcohol

1. Jun 22, 2009

### bigboss

1. The problem statement, all variables and given/known data

What is the initial temperature of copper if, 11 g aluminum at 200 C and 21 g of copper are dropped into 46 cm^3 of ethyl alcohol at 15 C. The final temperature of the system is 22 C.

2. Relevant equations

Q=McT

3. The attempt at a solution

My work : Qal+Qcu+Qea=0, and solved for the intial temperature. I got -130 C which was wrong. To find the mass of ethyl alcohol, i used volume and density. Volume is 790 kg/m^3

2. Jun 22, 2009

### mgb_phys

Re: Calorimetery

Try converting everything into the same units (eg kg)

3. Jun 22, 2009

### bigboss

Re: Calorimetery

i converted everything and got this forumla

m1 * s1 * t1 + m2 * s2 * t2 + = m1 * s1 * tf + m2 * s2 * tf + m3 * s3 * tf

m1= aluminum
m2=coppper
m3=ethtyl alcohol,

i just cant get the write answer.

4. Jun 22, 2009

### mgb_phys

Re: Calorimetery

In Q=mcT , 'T' is the change in temperature

5. Jun 22, 2009

### bigboss

Re: Calorimetery

yea, i took that into account, so i did heat loss=heat gained, and the heat lost was by the aluminum, and i know the ethyl alcohol gained heat, but im not sure what side the copper would go on

6. Jun 22, 2009

### mgb_phys

Re: Calorimetery

Al goes from 200 to 22
Cu goes from T to 22
Ethyl goes from 15 to 22

So
m_al * c_al * (200-22) + m_cu * c_cu * ( T-22) + m_eth * c_eth * (15-22) = 0