Exam 18: Heat and the First Law of Thermodynamics

Two liquids,A and B,are mixed together,and the resulting temperature is 22 ^$\circ$ C.If liquid A has mass m and was initially at temperature 35 ^$\circ$ C,and liquid B has mass 3m and was initially at temperature 11 ^$\circ$ C,calculate the ratio of the specific heats of A divided by B.

The specific heat of a gas is

The molar specific heat of copper is 24.5 J/(mol.K).The amount of heat needed to raise 126 g of copper by 2C ^$\circ$ is

A gas has a molar heat capacity at constant volume of 28.39 J/mol · K.Assume the equipartition theorem to be valid.How many degrees of freedom (including translational)are there for the molecules of this gas? (the ideal-gas law constant is R = 8.31 J/mol · K)

Besides Joule's classic experiment,another way of demonstrating the equivalence between mechanical energy and heat is the following: Put some lead shot into a glass tube,seal both ends of the tube,invert the tube quickly several times,and measure the temperature of the shot.If you assume that all the mechanical energy is converted into heat in the lead shot and that no heat is lost,what is the change in the temperature of the shot if the tube is 1.0 m long,there are 100 g of shot,and the tube is inverted 10 times? (The specific heat of lead is 0.128 kJ/kg · K.)

Body A has twice the mass and three times the specific heat of body B.They are supplied with equal amounts of heat.Body A experiences a temperature change $\Delta$ T.What change in temperature is experienced by body B?

The quantity of heat absorbed by a body is determined from the formula Q = cm(T_f - T_i).A certain metal has a specific heat c = 0.21 cal/g Cº and a mass m = 25.6 g.The initial temperature is T_i = 34.6ºC,and the final temperature T_f = 54.6ºC.The quantity of heat absorbed is

An ideal gas is heated so that it expands at constant pressure.The gas does work W.What heat is added to the gas?

The pressure of a mass of air at 20 ^$\circ$ C is halved adiabatically.If the ratio of C_p to C_v for air is 1.41,calculate the resulting temperature.

A small water reactor recently installed at Podunk College is operating at the boiling point of water due to the malfunctioning of the cooling system.The operators observe that the water boils away at the rate of 10 L/min.If they assume that all of the reactor energy is absorbed in the water,the power developed by the reactor is approximately

An ideal gas undergoes a cyclic process in which total (positive)work W is done by the gas.What total heat is added to the gas in one cycle?

Use the following to answer question: -Heat is added to a substance at a constant rate.The substance starts as a solid and is melted; the liquid is heated and vaporized; finally,the vapor is heated at constant volume.This process is shown in the graph.The specific heat at constant volume of the vapor can be found by

Use the following to answer the question: -The graph shows the temperature of a 1.0-g sample of material as heat is added to it.The material is initially a solid at 10ºC.The pressure remains constant,and there is no chemical change.The specific heat of the solid phase is

The temperature of water in the Gulf of Mexico can rise by about 20 ^$\circ$ F with the onset of the summer.However,the most significant temperature rise is confined to the top 2-3 meters of water.Assuming that it takes 45 days for the temperature to increase by 20 ^$\circ$ F,what is the average energy absorbed per day by water in a volume measuring 1 m $\times$ 1 m $\times$ 2.5 m?

A 4-kg mass of metal of unknown specific heat at a temperature of 600 ^$\circ$ C is dropped into 0.5 kg of ice and 0.5 kg of water both at 0 ^$\circ$ C.With no heat losses to the surroundings,the equilibrium temperature of the mixture is 85 ^$\circ$ C.Calculate the specific heat of the metal.

If the heat capacities of both ice and steam are 0.5 cal/g · Cº,the quantity of heat required to change 1 g of ice at -10ºC to steam at 120ºC is approximately

Use the following to answer the question: -The graph shows the temperature of a 1.0-g sample of material as heat is added to it.The material is initially a solid at 10ºC.The pressure remains constant,and there is no chemical change.The melting point temperature is

Use the following to answer the question: -An ideal gas initially at 50ºC and pressure P₁ = 100 kPa occupies a volume V₁ = 3 L.It undergoes a quasi-static,isothermal expansion until its pressure is reduced to 50 kPa.How much work was done by the gas during this process? R = 8.314 J/mol·K = 8.206 L·atm/mol·K.

In a system composed of an ideal gas contained in a cylinder fitted with a piston,a reversible adiabatic expansion causes the temperature of the gas to drop because

How much internal energy is contained in 1 mole of monatomic gas at STP?