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Problem 8a
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 10d
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 11
Problem 12b
(b) Why does increasing the temperature cause a solid substance to change in succession from a solid to a liquid to a gas?
- (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?
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?
- (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 19
Problem 19a
Predict the chemical formula of the ionic compound formed between the following pairs of elements: (a) Al and F
Problem 21a
(a) According to the first law of thermodynamics, what quantity is conserved?
Problem 21c
(c) By what means can the internal energy of a closed system increase?
- (a) Write an equation that expresses the first law of thermodynamics in terms of heat and work. (b) Under what conditions will the quantities q and w be negative numbers?
Problem 22
Problem 23a
Calculate ΔE and determine whether the process is endothermic or exothermic for the following cases: (a) q = 0.763 kJ and w = -840 J.
Problem 24a,b
For the following processes, calculate the change in internal energy of the system and determine whether the process is endothermic or exothermic: (a) A balloon is cooled by removing 0.655 kJ of heat. It shrinks on cooling, and the atmosphere does 382 J of work on the balloon. (b) A 100.0-g bar of gold is heated from 25 °C to 50 °C during which it absorbs 322 J of heat. Assume the volume of the gold bar remains constant.
Problem 25a
A gas is confined to a cylinder fitted with a piston and an electrical heater, as shown here:
Suppose that current is supplied to the heater so that 100 J of energy is added. Consider two different situations. In case (1) the piston is allowed to move as the energy is added. In case (2) the piston is fixed so that it cannot move. (a) In which case does the gas have the higher temperature after addition of the electrical energy?
Problem 25b
A gas is confined to a cylinder fitted with a piston and an electrical heater, as shown here:
Suppose that current is supplied to the heater so that 100 J of energy is added. Consider two different situations. In case (1) the piston is allowed to move as the energy is added. In case (2) the piston is fixed so that it cannot move. (b) Identify the sign (positive, negative, or zero) of q and w in each case?
Problem 26a
Consider a system consisting of two oppositely charged spheres hanging by strings and separated by a distance r1, as shown in the accompanying illustration. Suppose they are separated to a larger distance r2, by moving them apart. (a) What change, if any, has occurred in the potential energy of the system?
Problem 27a
Imagine that you are climbing a mountain. Which of the following are state functions? a. The distance you walk during your climb to the top
Problem 27b
Imagine that you are climbing a mountain. Which of the following are state functions? b. The change in elevation during the climb
Problem 31
During a normal breath, our lungs expand about 0.50 L against an external pressure of 1.0 atm. How much work is involved in this process (in J)?
Problem 32
How much work (in J) is involved in a chemical reaction if the volume decreases from 5.00 to 1.26 L against a constant pressure of 0.857 atm?
- (a) Under what condition will the enthalpy change of a process equal the amount of heat transferred into or out of the system? (b) During a constant-pressure process, the system releases heat to the surroundings. Does the enthalpy of the system increase or decrease during the process? (c) In a constant-pressure process, _x001F_H = 0. What can you conclude about _x001F_E, q, and w?
Problem 34
- Assume that 2 moles of water are formed according to the following reaction at constant pressure (101.3 kPa) and constant temperature (298 K): 2 H2(g) + O2(g) → 2 H2O(l). (b) Calculate _x001F_E for the reaction using your answer to (a).
Problem 35
- Suppose that the gas-phase reaction 2 NO(g) + O2(g) → 2 NO2(g) were carried out in a constant-volume container at constant temperature. (a) Would the measured heat change represent _x001F_H or _x001F_E? (b) If there is a difference, which quantity is larger for this reaction? (c) Explain your answer to part (b).
Problem 36
Problem 38
A gas is confined to a cylinder under constant atmospheric pressure, as illustrated in Figure 5.4. When 0.49 kJ of heat is added to the gas, it expands and does 214 J of work on the surroundings. What are the values of H and E for this process?