Write an equation that represents the first law of thermodyn

Write an equation that represents the first law of thermodynamics. Identify all terms and state any assumptions. A 50 cm^3 mixture of 20% helium and 80% argon, by volume, at 300 K is heated in a piston at constant pressure until the volume doubles. Find the work done on the surroundings (kJ).

Solution

First law of Thermodynamics says that, \"Energy can neither be created nor destroyed. It can be only transfer from one form to another form.\"

According to that, first law is the application of the conservation of energy principle to heat and thermodynamic processes that says \" The Change in internal enegy of a system is equal to the heat added to the system minus work done by the system.\"

U = Q - W

U = Change in internal enegy of a system

Q = Heat added to the system

W = Work done by the system

The first law makes use of concepts of internal energy, heat, and system work. It is nowdays used extensively in the heat engines discussion. The standard unit for all these quantities would be the joule, but many times expressed in calories or BTU.

Here +/- shows how system is treated like +W means as the work done on the system instead of work done by the system and vice versa for the heat Q. So, Sign conversion is very important in this equation.