AP Chemistry Rate Mechanisms and Catalyst

A kinetics experiment is set up to collect the gas that is generated when a sample of chalk, consisting primarily of solid CaCO_3, is added to a solution of ethanoic acid, CH₃COOH. The rate of reaction between CaCO₃ and CH₃COOH is determined by measuring the volume of gas generated at 25°C and 1 atm as a function of time. Which of the following experimental conditions is most likely to increase the rate of gas production?

• Decreasing the volume of ethanoic acid solution used in the experiment

• Decreasing the concentration of the ethanoic acid solution used in the experiment

• Decreasing the temperature at which the experiment is performed

• Decreasing the particle size of the CaCO₃ by grinding it into a fine powder

Tags

NGSS.HS-PS1-5

Consider the mechanism for the reaction 2NO + O₂ --> 2NO_2. Which of the following statements is true?

• Step 1 represents a unimolecular reaction.

• Increasing the concentration of NO will decrease the overall rate of the reaction.

• Raising the temperature will have no effect on the numerical value of the rate constant.

• The rate law that is consistent with the mechanism is rate=k[NO]²[O₂]

Tags

NGSS.HS-PS1-5

A proposed mechanism for the destruction of ozone gas in the stratosphere is represented above. Which of the following is evidence that the mechanism is occurring?

• The presence of Cl(g) increases the rate of the overall reaction.

• The presence of Cl(g) decreases the rate of the overall reaction.

• The presence of Cl(g) increases the equilibrium constant of the overall reaction.

• The presence of Cl(g) decreases the equilibrium constant of the overall reaction.

Tags

NGSS.HS-PS1-2

NGSS.HS-PS1-5

A sample of N₂O₅ was placed in an evacuated container and the reaction (2N₂O₅ --> 4NO + O₂) occured. The value of P_N2O5, the partial pressure of N₂O_5, was measured during the reaction and recorded in the table. Which of the following correctly describes the reaction?

• The decomposition of N₂O_{5 a} zero-order reaction

• The decomposition of N₂O_{5 a} first-order reaction

• The decomposition of N₂O_{5 a} second-order reaction

• The overall reaction order is 3

Tags

NGSS.HS-PS1-5

The graph shows the speed distribution of molecules in a sample of a gas at a certain temperature. Which of the following graphs shows the speed distribution of the same molecules at a lower temperature? (as a dashed curve)

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Tags

NGSS.HS-PS1-5

A reaction (X₂ + Y₂--> X₂Y₂) has the rate law, rate=k[X₂]. A chemist proposes two different possible mechanisms for the reaction which are given in the image. Based on the information, which of the following is true?

• Only mechanism 1 is consistent with the rate law.

• Only mechanism 2 is consistent with the rate law.

• Both mechanism 1 and 2 are consistent with the rate law.

• Neither mechanism 1 nor mechanism 2 is consistent with the rate law.

Tags

NGSS.HS-PS1-5

Consider the reaction represented by the equation 2X + 2Z --> X₂Z₂. During a reaction in which a large excess of reactant X was present, the concentration of reactant Z was monitored over time. A plot of the natural logarithm of the concentration of Z versus time is shown in the figure above. The order of the reaction with respect to the reactant Z is

• zero order

• first order

• second order

• third order

The equation (XY₂ --> X + Y₂) represents the decomposition of XY₂. The diagram below shows two reaction profiles (path one and path two) for the decomposition of of XY₂. Which of the following most likely accounts for the difference between reaction path one and reaction path two?

• A higher temperature in path one

• A higher temperature in path two

• The presence of a catalyst in path one

• The presence of a catalyst in path two

Tags

NGSS.HS-PS1-4

NGSS.HS-PS1-5

The equation (XY₂ --> X + Y₂) represents the decomposition of XY₂. The diagram below shows two reaction profiles (path one and path two) for the decomposition of of XY₂. Which of the following best describes the flow of heat when 1.0 mol of XY₂ decomposes?

• 50 kJ of heat is transferred to the surroundings.

• 50 kJ of heat is transferred from the surroundings.

• 100 kJ of heat is transferred to the surroundings.

• 100 kJ of heat is transferred from the surroundings.

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-4

The reaction (NO + NO₃--> 2NO₂) has the rate law, rate=k[NO][NO₃]. A scientist correctly calculates the rate of collisions between NO and NO₃ that have sufficient energy to overcome the activation energy. The observed reaction rate is only a small fraction of the calculated collision rate. Which of the following best explains the discrepancy?

• The energy of collisions between two reactant particles is frequently absorbed by collision with a third particle.

• The two reactant particles must collide with a particular orientation in order react.

• The activation energy for a reaction is dependent on the concentrations of the reactant particles.

• The activation energy for a reaction is dependent on the temperature.

Tags

NGSS.HS-PS1-5