in a chemical reaction experiment using calorimeter, which is the system and which is the surrounding?

Having just invented a new type of calorimeter, Dr. Cox needs to determine the heat capacity of the calorimeter.  She carries out the following experiment to do this: Her empty calorimeter is at a temperature of 25.0ºC.  She adds 32.502 grams of water at a temperature of 72.5ºC to the empty calorimeter and the final temperature of the calorimeter and the water is 39.5ºC.   Based on this experiment, what is the heat capacity of her calorimeter assuming units of J/ºC? Enter your answer with at least 3 sig figs.

A gaseous fuel mixture contains 24.2% methane (CH4), 40.5% ethane (C₂H6) and the rest propane (C3H8) by volume. When the fuel mixture contained in a 1.56 L tank, stored at 754 mmHg and 298 K, undergoes complete combustion, how much heat is emitted? (Assume that the water produced by the combustion is in the gaseous state.) Express your answer with the appropriate units. μÅ Value Submit Units Request Answer ?

A piston compresses the air in the cylinder by doing 71.0  J of work on the air. As a result, the air gives off 159.0  J of heat to the surroundings. If the system is the air in the cylinder, what is the change in its internal energy?