Question

At what temperature will the water in each of these jars reach thermal equilibrium?

Answer 1

If you are working with closed systems, you need to know the mass of water, its initial temperature, the specific heat of the water (which is 1 cal / g °C), the mass of the environment with which the water is in contac, its initial temperature and the specific heat.

Then you use this formula:

mass of water * 1 cal /g °C * (Equilibrium temperature - initial temperature of the environment) = mass of the environment * Cs of the environment * ( Initial temperature  of the environment - Equilibrium temperature)

From that you can solve for the Equilibrium temperature.

If it is not a closed system, buth the jars are in contact with an indefinite large amount of air, then the jars will reach the temperature of the air that surrounds the jars and that will be the thermal equilibrium.