Gen Chem Ch. 12-13 Quiz Answers

For a certain reaction at 25-degrees C, the value of K is 1.2 x 10⁻². At 50-degrees C, the value of K is 3.4 x 10⁻³. This means that the reaction is... A. Exothermic B. Endothermic C. Very favorable at a higher temperature D. More information needed E. None of selections A-D are correct

*A. Exothermic* - At a higher temperature, the value of k is less than that of a lower temperature. That means there are more factors on the product side (heat) bringing down the overall value of k

Consider the following system at equilibrium: N₂(g) + 3H₂(g) <-> 2NH₃(g) + 92.94 kJ If the volume of the container is doubled, what is the effect on the reaction? A. Shifts to the right (toward products) B. Shifts to the left (toward reactants) C. There is no change to the equilibrium

*B. Shifts to the left (toward reactants)* - *There are more moles of gas on the left side*

In general, the value of the equilibrium constant for a chemical reaction does NOT depend on A. The temperature of the reaction vessel B. The initial amounts of reactants present C. The total pressure of the reaction vessel D. The volume of the reaction vessel E. The rate constants of the forward and reverse reactions

*B. The initial amounts of reactants present*

The reaction (3A + 4B -> products) is first order in A and third order in B. What is the *overall* order of the reaction? A. 1 B. 3 C. 4 D. 5 E. 7

*C. 4* - *First order plus third order = 4*

Which of the following is true about chemical equilibrium? A. It is microscopically and macroscopically static B. It is microscopically and macroscopically dynamic C. It is microscopically static and macroscopically dynamic D. It is microscopically dynamic and macroscopically static

*D. It is microscopically dynamic and macroscopically static* - It *appears* to be static macroscopically

Consider the following system at equilibrium: N₂(g) + 3H₂(g) <-> 2NH₃(g) + 92.94 kJ If the temperature is decreased, what is the effect on the reaction? A. Shifts to the right (toward products) B. Shifts to the left (toward reactants) C. There is no change to the equilibrium

A. Shifts to the right (toward products) - Heat is a product of the reaction

Consider the following system at equilibrium: N₂(g) + 3H₂(g) <-> 2NH₃(g) + 92.94 kJ If NH₃(g) is added, what is the effect on the reaction? A. Shifts to the right (toward products) B. Shifts to the left (toward reactants) C. There is no change to the equilibrium

B. Shifts to the left (toward reactants)

The reaction (2A + 5B -> products) is third order in A and first order in B. What is the rate law for this equation? A. rate = k[A]²[B]⁵ B. rate = k[A]³[B] C. rate = k[A][B]³ D. rate = k[A]⁵[B]² E. rate = k[A]²/⁷[B]⁵/⁷

B. rate = k[A]³[B] - *Third order in A and first order in B*

Consider the reaction X -> Y + Z. Which of the following is a possible rate law for this equation? A. Rate = k[X][Y][Z] B. Rate = k[Y][Z] C. Rate = k[X]² D. Rate = k[X][Y] E. Rate = k[Z]

C. Rate = k[X]² - When determining a rate law, only the reactants are considered - This is because since the rate-determining step determines the rate law, and that step can only be on the reactant side, only reactants can be considered

Consider the following system at equilibrium: N₂(g) + 3H₂(g) <-> 2NH₃(g) + 92.94 kJ If in a rigid container, some Ar(g) is added, what is the effect on the reaction? A. Shifts to the right (toward products) B. Shifts to the left (toward reactants) C. There is no change to the equilibrium

C. There is no change to the equilibrium - Partial pressures are unchanged because Ar(g) is an inert gas

Which of the following statements is false? A. At equilibrium, the concentrations of all species are constant B. The value of the equilibrium constant depends on the temperature C. At equilibrium, the forward and reverse reactions are happening at the same rate D. At equilibrium, the concentrations of all species are equal E. Pure solids are not included in the equilibrium constant expression

D. At equilibrium, the concentrations of all species are equal

Which of the following is true for a system whose equilibrium constant is relatively large? A. It will take a short time to reach equilibrium B. It will take a long time to reach equilibrium C. The equilibrium lies to the left (reactants) D. The equilibrium lies to the right (products)

D. The equilibrium lies to the right (products) - When k>>1, equilibrium lies to the right

Consider the following rate law: Rate = k[A]ⁿ[B]ᵐ. How are the exponents n and m determined? A. By using information in the balanced chemical equation B. By educated guess C. By using the subscripts for the chemical formula D. By using the coefficients of the chemical formulas E. By experiment

E. By experiment