G = H – TS
Nt/No = 0.5n n= t/t1/2
Multiple choice (2 points each)
- Calculate ∆H for the reaction of sulfur dioxide with oxygen. 2SO2 (g) + O2 (g) → 2SO3 (g)
(∆H0f SO2 (g) = –296.8 kJ/mol; ∆H0f SO3 (g) = –395.7 kJ/mol)
- –98.9 kJ d. 197.8 kJ
- –197.8 kJ e. Not enough information is given.
- +98.9 kJ
- Wich of the following statements is true?
- In an endothermic process heat is transferred from the surroundings to the system.
- In an exothermic process heat is transferred from the surroundings to the system.
- The surroundings will feel cooler in an exothermic process.
- The surroundings will feel warmer in an endothermic process.
- If the rate of disappearance of H2 is 3.00 M/s, calculate the rate of NH3 appearance. Given: N2 + 3H2 → 2NH3
- 2.00 M/s d. 4.50 M/s
- 1.00 M/s e. 1.50 M/s
- 3.00 M/s
- If plutonium-246 decays with a half-life of 200.0 years, what percentage of a sample would remain after 600.0 years?
- 33.3% d. 6.25%
- 25.0% e. 8.00%
- A reaction is zero order in reactant A and second order in reactant B. What happens to the reaction rate when the concentrations of both reactants are doubled? a. The reaction rate remains the same.
- The reaction rate increases by a factor of two.
- The reaction rate increases by a factor of four.
- The reaction rate increases by a factor of eight.
- Collision theory assumes that the rate of a reaction depends on __________
- the energy of collisions.
- the orientation of colliding molecules.
- the energy of collisions and the orientation of colliding molecules.
- the change in energy between the products and the reactants.
- the change in free energy between the reactants and products.
- As energy is added to a substance, the temperature remains constant. How may the substance be changing?
- From a gas to a solid c. From a liquid to a solid
- From a liquid to a gas d. In the amount of kinetic energy
- The rate law of the overall reaction A+B → C is rate = k[A]2. Which of the following will not increase the rate of the reaction? a. increasing the concentration of reactant A
- increasing the temperature of the reaction
- increasing the concentration of reactant B
- adding a catalyst for the reaction
- all of these will increase the rate.
- The following graph shows the kinetics for the reaction of oxygen with hydrogen to form water: O2 (g) + 2 H2(g) →2H2O(g). Which curve is oxygen?
- In the process of dissolving NH4 (s) in water, the entropy increases. This means that the sign of ΔS is ________, and that the randomness of the system ________. a. undetermined; increases d. negative; decreases
- positive; decreases e. negative; increases
- positive; increases
- When 45 g of metal, at 25C, are dropped into 100.0 g of water, the alloy absorbs 956 J of heat. If the final temperature of the alloy is 37C, what is the specific heat? (1 cal = 4.184J)
- 0.423 cal/gC c. 9.88 cal/gC
- 1.77 cal/gC d. 48.8 cal/gC
- Given the thermochemical equation 2C(s) + 2O2(g) → 2CO2(g) ΔH = −787 kJ
What is the ΔH for the reaction CO2(g) → C(s) + O2(g)?
- −0.00250 kJ d. +394 kJ
- −394 kJ e. -787 kJ
- +0.00250 kJ
- Consider the reaction energy diagram below to provide answers to the following questions. (4 points)
- Which line represents the value of G of the forward reaction? _____________
- Which line represents the activation energy of the forward reaction? _______________
- Is this reaction exergonic or endergonic? ____________________
- What does the letter B represent? _________________________
- Identify the following as an endothermic or exothermic process. (3 points)
- alcohol evaporating _____________
- ice melting _____________________
- steam condensing ________________
- Write the nuclear equations for the following: (6 points)
- Cobalt-56 decays by emitting a positron.
- The alpha decay of polonium-218
- The beta decay of lead-210
Part IIII. Please provide thoughtful answers in the space provided below. If you do not show your work, no partial credit can be given.
- Find H° for the reaction B2H6(g) + 6 Cl2(g) 2 BCl3(g) + 6 HCl(g), using the following thermochemical data. (6 points)
BCl3(g) + 3 H2O(l) H3BO3(g) + 3 HCl(g) H = -112.5 kJ
B2H6(g) + 6 H2O(l) 2 H3BO3(g) + 6 H2(g) H = -493.4 kJ
1/2 H2(g) + 1/2 Cl2(g) HCl(g) H = -92.3 kJ
- How much energy is needed to convert 64.0 g of ice at -4.00 C to water at 55.0 C?
Enthalpy of fusion
Enthalpy of vaporization
Specific heat of solid H2O (ice)
Specific heat of liquid H2O (water)
Specific heat of gaseous H2O (steam)
- Phosphorous-32 is a radioactive isotope used as a tracer in the liver. How much phosphorous 32 was originally used if there is only 3.50 mg left in a sample after 12 days? (The half-life of phosphorous-32 is 14.3 days) (4 points)
Nt/No = 0.5n n= t/t1/2
- Consider the reaction: SO2 + O3 → SO3 + O2. A rate study was conducted at 298K. The data that were obtained are shown in the table. (6 points)
Initial rate, M/s
- What is the rate law for this reaction?
- Determine the value and the units of the rate constant, k.
- Methanol, CH3OH (molar mass = 32.03 g/mol), is an efficient fuel with a high-octane rating that can be produced from coal and hydrogen. (6 points)
CH3OH (g) + 3/2 O2 (g) → CO2 (g) + 2 H2O (l) ∆H = -764 kJ
- Find the heat evolved when 95.0 g CH3OH (g) burns in excess oxygen.
- What mass of O2 is consumed when 975 kJ of heat is given off?
Bonus: Thanksgiving Trivia (3 points)
- Which Indian tribe taught the Pilgrims how to cultivate the land and were invited to the Thanksgiving meal?
- Apache c. Cherokee
- Approximately how many turkeys are eaten each year on Thanksgiving in the United States?
- 20 million c. 100 million
- 46 million
- Which American football team has played on every Thanksgiving since 1945?
- Buffalo Bills c. Detroit Lions
- Green Bay Packers