Back
- Two positively charged spheres, each with a charge of 2.0 * 10^-5 C, a mass of 1.0 kg, and separated by a distance of 1.0 cm, are held in place on a frictionless track. (b) If the spheres are released, will they move toward or away from each other? (c) What speed will each sphere attain as the distance between the spheres approaches infinity?
Problem 1
Problem 1a
Two positively charged spheres, each with a charge of 2.0⨉10-5 C, a mass of 1.0 kg, and separated by a distance of 1.0 cm, are held in place on a frictionless track. (a) What is the electrostatic potential energy of this system?
- Identify the force present and explain whether work is done when (a) an electron moves in a circle at a fixed distance from a proton, (b) an iron nail is attracted by and pulled onto a magnet.
Problem 2
Problem 2a
The accompanying photo shows a pipevine swallowtail caterpillar climbing up a twig. (a) As the caterpillar climbs, its potential energy is increasing. What source of energy has been used to effect this change in potential energy?
- Consider the accompanying energy diagram. (a) Does this diagram represent an increase or decrease in the internal energy of the system?
Problem 3
Problem 4a
The contents of the closed box in each of the following illustrations represent a system, and the arrows show the changes to the system during some process. The lengths of the arrows represent the relative magnitudes of q and w. (a) Which of these processes is endothermic?
Problem 5a
Imagine that you are climbing a mountain. (a) Is the distance you travel to the top a state function?
Problem 5b
Imagine that you are climbing a mountain. (b) Is the change in elevation between your base camp and the peak a state function?
- Under constant-volume conditions, the heat of combustion of naphthalene (C10H8) is 40.18 kJ/g. A 2.50-g sample of naphthalene is burned in a bomb calorimeter. The temperature of the calorimeter increases from 21.50 to 28.83 °C. (b) A 1.50-g sample of a new organic substance is combusted in the same calorimeter. The temperature of the calorimeter increases from 21.14 to 25.08 °C. What is the heat of combustion per gram of the new substance?
Problem 6
Problem 6a
The diagram shows four states of a system, each with different internal energy, E. (a) Which of the states of the system has the greatest internal energy?
Problem 6c
The diagram shows four states of a system, each with different internal energy, E. (c) Write an expression for the difference in energy between State C and State D.
- You may have noticed that when you compress the air in a bicycle pump, the body of the pump gets warmer. (c) Based on your answers to parts (a) and (b), can you determine the sign of _x001F_E for compressing the air in the pump? If not, what would you expect for the sign of _x001F_E? What is your reasoning?
Problem 7
Problem 8a
Imagine a container placed in a tub of water, as depicted in the accompanying diagram. (a) If the contents of the container are the system and heat is able to flow through the container walls, what qualitative changes will occur in the temperatures of the system and in its surroundings? From the system's perspective, is the process exothermic or endothermic?
Problem 9a
In the accompanying cylinder diagram, a chemical process occurs at constant temperature and pressure. (a) Is the sign of w indicated by this change positive or negative?
Problem 10b
(b) Why does increasing the temperature cause a solid substance to change in succession from a solid to a liquid to a gas?
Problem 11d
Consider the two diagrams that follow. (d) Would similar relationships hold for the work involved in each process?
- Consider the combustion of a single molecule of CH4(g), forming H2O(l) as a product. (b) A typical X-ray light source has an energy of 8 keV (see inside back cover for conversion between eV and J). Is the energy released by the combustion of a CH4 molecule larger or smaller than the energy of an X-ray from this source?
Problem 12
- (a) What is the electrostatic potential energy (in joules) between an electron and a proton that are separated by 230 pm? (b) What is the change in potential energy if the distance separating the electron and proton is increased to 1.0 nm? (c) Does the potential energy of the two particles increase or decrease when the distance is increased to 1.0 nm?
Problem 13
Problem 14a
(a) What is the electrostatic potential energy (in joules) between two electrons that are separated by 62 pm?
Problem 14b
(b) What is the change in potential energy if the distance separating the two electrons is increased to 1.0 nm?
Problem 14c
(c) Does the potential energy of the two particles increase or decrease when the distance is increased to 1.0 nm?
- (b) The force of gravity acting between two objects is given by the equation F = G * (m1 * m2) / d^2, where G is the gravitational constant, G = 6.674 * 10^-11 N*m^2/kg^2, m1 and m2 are the masses of the two objects, and d is the distance separating them. What is the gravitational force of attraction (in Newtons) between the electron and proton? (c) How many times larger is the electrostatic force of attraction?
Problem 15
Problem 15a
(a) The electrostatic force (not energy) of attraction between two oppositely charged objects is given by the equation F = k (Q1Q2/d2) where k = 8.99⨉109N-m2/C2, Q1 and Q2 are the charges of the two objects in Coulombs, and d is the distance separating the two objects in meters. What is the electrostatic force of attraction (in Newtons) between an electron and a proton that are separated by 1⨉102 pm?
- Use the equations given in Problem 5.15 to calculate: (a) The electrostatic force of repulsion for two electrons separated by 75 pm. (b) The gravitational force of attraction for two electrons separated by 75 pm. (c) If allowed to move, will the electrons be repelled or attracted to one another?
Problem 16
Problem 17
A sodium ion, Na+, with a charge of 1.6⨉10-19 C and a chloride ion, Cl - , with charge of -1.6⨉10-19 C, are separated by a distance of 0.50 nm. How much work would be required to increase the separation of the two ions to an infinite distance?
Problem 18
A magnesium ion, Mg2+, with a charge of 3.2⨉10-19 C and an oxide ion, O2-, with a charge of -3.2⨉10-19 C, are separated by a distance of 0.35 nm. How much work would be required to increase the separation of the two ions to an infinite distance?
- Identify the force present and explain whether work is being performed in the following cases: (a) You lift a book off the top of a desk. (b) Air is compressed in a bicycle pump.
Problem 19
- (a) Which of the following cannot leave or enter a closed system: heat, work, or matter? (b) Which cannot leave or enter an isolated system? (c) What do we call the part of the universe that is not part of the system?
Problem 21
Problem 22a
In a thermodynamic study, a scientist focuses on the properties of a solution in an apparatus as illustrated. A solution is continuously flowing into the apparatus at the top and out at the bottom, such that the amount of solution in the apparatus is constant with time. (a) Is the solution in the apparatus a closed system, open system, or isolated system?
Problem 22b
In a thermodynamic study, a scientist focuses on the properties of a solution in an apparatus as illustrated. A solution is continuously flowing into the apparatus at the top and out at the bottom, such that the amount of solution in the apparatus is constant with time. (b) If the inlet and outlet were closed, what type of system would it be
