Chemical Equilibrium

Consider the following reaction: CaCO3(s) ↔ CO2(g) + CaO(s) . What will happen to the system if more CaCO3 is added? A) nothing B) the amount of CaCO3 will decrease C) less CaO will be produced D) the pressure will increase E) the concentration of CO2 will decrease

A) Nothing

Which of the following is (are) unaffected by reversing the direction in which a chemical equation is written? A) The equilibrium concentrations B) The equilibrium constant value C) The mass action expression D) All of the above

A) The equilibrium concentrations

Consider the reaction of hydrogen gas and oxygen gas to produce liquid water. Which of the following is true? A) The position of the equilibrium is unaffected by the addition of liquid water. B) Removing some of the hydrogen gas has no effect on the position of the equilibrium. C) Reducing the volume of the reaction vessel has no effect on the position of the equilibrium. D) None of the above are true.

A) The position of the equilibrium is unaffected by the addition of liquid water.

Consider the following reaction: 4HCl(g) + O2(g) ↔ 2H2O(g) + 2Cl2(g) with DH = -114.4 kJ One way to decrease the amount of chlorine present at equilibrium is A) removing the water vapor while it is being formed. B) raising the temperature. C) adding more hydrogen chloride. D) decreasing the volume of the reaction vessel. E) none of the above.

B) raising the temperature.

Calculate the equilibrium constant for the process AÛB, given the following equilibrium concentrations: [N2O4] = 0.0427 M ; [NO2] = 0.0141 M A) 6.60x10-1 B) 215 C) 0.00466 D) 0.330 E) 3.03

C) 0.00466 Equilibrium constant = [no2]^2/[N2O4]

Chemical reactions take place because the molecules involved in a reaction A) break apart spontaneously, then recombine. B) exist only above a certain temperature. C) collide with each other and break bonds. D) are moving very fast. E) are very unstable.

C) collide with each other and break bonds.

The concentrations of pure solids are normally excluded in an equilibrium constant expression because A) these substances do not participate in the processes that are at equilibrium. B) at the time the equilibrium is established, their absolute amounts have not varied from the original amounts. C) the concentration of a pure solid remains essentially constant throughout the reaction. D) they do not play a vital role in the rate-determining step of the reaction. E) none of the above.

C) the concentration of a pure solid remains essentially constant throughout the reaction.

•The reaction N2O4(g) ↔ 2NO2(g) is endothermic. Which of the following is true? A) Decreasing the pressure drives the reaction to the right. B) Increasing the temperature drives the reaction to the right. C) Decreasing the volume drives the reaction to the left. D) All of the above.

D

The reaction of hydrogen gas with nitrogen gas to produce ammonia gas is exothermic. Which of the following is true? A) Increasing the pressure of the reaction system will increase production of ammonia. B) Condensing the ammonia gas produced into liquid will increase the production of ammonia. C) Decreasing the temperature of the reaction will increase the production of ammonia. D) All of the above.

D) All of the above.

Which of the following statements is true of a catalyst? A) Its concentration stays constant throughout the reaction B) it increases the rate of a reaction C) it provides a new pathway for the reaction D) all of the above E) none of the above

D) all of the above

•The reaction of oxygen with hemoglobin produces oxyhemoglobin, which carries oxygen to body tissues. At high altitudes the following results are seen A) the lower oxygen pressure causes the equilibrium to shift away from oxyhemoglobin. B) "altitude sickness" can occur in unacclimated individuals. C) people who live in higher altitudes develop higher levels of hemoglobin to function normally. D) all of them.

D) all of them.

For reactions in gas phase, a relationship can be established between Kc and Kp. For which of the following processes will the two constants have the same numerical value? A) formation of water vapor from hydrogen and oxygen B) formation of carbon dioxide from carbon monoxide and oxygen C) synthesis of ammonia from hydrogen and nitrogen D) decomposition of hydrogen iodide into hydrogen and iodine gas E) conversion of nitrogen dioxide into dinitrogen tetroxide

D) decomposition of hydrogen iodide into hydrogen and iodine gas

At equilibrium A) the rate constants for the forward and reverse reactions are equal. B) the reaction ends. C) all reactants have been converted to products. D) the forward and reverse rates are equal. E) none of the above.

D) the forward and reverse rates are equal.

Consider the chemical change AÛB. After the reaction starts, but before the system reaches equilibrium, the only process that takes places is A being converted into B. A) True B) False

False

The value of the equilibrium constant is not affected by the concentrations of A) pure solids and liquids. B) gases. C) aqueous solutions. D) all of the above.

Pure Solid and Liquids.

If a reaction is endothermic, then the equilibrium constant is higher at higher temperature. A) True B) False

True

The value of an equilibrium constant depends on A) the rate of the reaction. B) how the equilibrium equation is balanced. C) the starting concentrations of the reactants. D) all of the above.

how the equilibrium equation is balanced.

For a particular set of concentrations, if the value of Q is much greater than the value of the equilibrium constant, K, for a reaction, then A) the initial rate of the reaction will be very fast, but will slow as equilibrium is approached. B) the reaction will proceed to the right, but the rate cannot be determined from the Q or K. C) the reaction will proceed to the left, but the rate cannot be determined from the Q or K. D) the reaction will proceed to make more products if the value of K is much greater than one.

the reaction will proceed to the left, but the rate cannot be determined from the Q or K.

•If an equilibrium for a reaction is said to lie to the right then the equilibrium constant A) is a negative value. B) is a positive value less than one. C) is a positive value greater than one. D) is equal to one.

C) is a positive value greater than one.

Consider the following reaction: 2H2(g) + 2Cl2(g) ↔ 2HCl(g) + heat . What will happen to the system if the volume of the reaction vessel is decreased? A) more HCl will dissociate B) amounts of H2 and Cl2 will decrease C) less heat is produced D) all of the above E) none of the above

B) amounts of H2 and Cl2 will decrease