# Thermal Physics Question

1. Nov 18, 2007

### gamx

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

An oxygen supply system mixes oxygen at 105 K and room air at 307 K at equal mass flow rates. What is the temperature of the resulting mixture in K? (c of oxygen = 918 J/kgK, c of air = 1012 J/kgK)

2. Relevant equations

$$Q=mc\Delta T$$ and $$Q=mL_f$$
3. The attempt at a solution

(105 x 918 + 1012 x 307) / (918 + 1012) = 210 K ( not a single inkling about the validity of the answer ) -_- . The inadequancy of my lecture notes really leaves me clueless =/

Last edited: Nov 18, 2007
2. Nov 18, 2007

### Oerg

firstly, we must define delta T clearly. delta T is the change in temperature of both mixtures, and we can define delta T as the temepreature change from 105K, and then the temperature change for the room air is (307-105)=202K, 202-deltaTK.

Equate both equations together in the first equation you gave and you have the answer.