Exam 6: Thermochemistry: Energy Flow and Chemical Change

A system initially has an internal energy E of 501 J. It undergoes a process during which it releases 111 J of heat energy to the surroundings, and does work of 222 J. What is the final energy of the system, in J?

The only way in which a system can do work on the surroundings is by expansion against the external pressure.

A system receives 575 J of heat and delivers 425 J of work. Calculate the change in the internal energy, E, of the system.

For all processes, both q and w will have the same sign.

Which one of the following statements about standard states is incorrect?

A system that does no work but which receives heat from the surroundings has

Cold packs, whose temperatures are lowered when ammonium nitrate dissolves in water, are carried by athletic trainers when transporting ice is not possible. Which of the following is true of this reaction?

Which one of the following is a correct formation reaction?

When Karl Kaveman adds chilled grog to his new granite mug, he removes 10.9 kJ of energy from the mug. If it has a mass of 625 g and was at 25°C, what is its new temperature? Specific heat capacity of granite = 0.79 J/(g·K)

Calculate q when 28.6 g of water is heated from 22.0°C to 78.3°C.

In a reaction with high energy reactants and low energy products, q is negative.

a. Define, or explain fully what is meant by the standard enthalpy of formation of a substance, H°_f.. b. What is the standard state of the element oxygen? c. Write down in full the formation reaction for liquid ethanol, C₂H₅OH(l). The equation should be balanced and should indicate the physical state of each substance.

An ideal gas (the system) is contained in a flexible balloon at a pressure of 1 atm and is initially at a temperature of 20.°C. The surrounding air is at the same pressure, but its temperature is 25°C. When the system has equilibrated with its surroundings, both systems and surroundings are at 25°C and 1 atm. In changing from the initial to the final state, which one of the following relationships regarding the system is correct?

Standard heats (enthalpies) of formation of compounds, H°_f, may be positive or negative.

The dissolution of barium hydroxide in water is an exothermic process. Which of the following statements is correct?

A system delivers 225 J of heat to the surroundings while delivering 645 J of work. Calculate the change in the internal energy, E, of the system.

A piece of copper metal is initially at 100.0°C. It is dropped into a coffee cup calorimeter containing 50.0 g of water at a temperature of 20.0°C. After stirring, the final temperature of both copper and water is 25.0°C. Assuming no heat losses, and that the specific heat (capacity) of water is 4.18 J/(g·K), what is the heat capacity of the copper in J/K?

The enthalpy (H) of liquid water is greater than that of the same quantity of ice at the same temperature.

Clearly state the thermodynamic standard state of a. an element or compound. b. a solute.

A system which undergoes an adiabatic change and has work done on it by the surroundings has