Chemistry Reaction Rates and Equilibrium

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Questions and Answers

What is the primary function of a catalyst in a chemical reaction?

To increase the activation energy required for the reaction

To provide a source of energy for the reaction

To increase the speed of the reaction without being consumed (correct)

To undergo a chemical change during the reaction

Which type of catalyst operates in a different phase than the reactants?

Homogeneous catalyst

Biocatalyst

Autocatalyst

Heterogeneous catalyst (correct)

How will the rate of reaction change if the concentration of reactants A and B is increased three times in the equation Rate = k · [A]² · [B]?

Remains unchanged

Increases by 27 times (correct)

Increases by 6 times

Increases by 9 times

What effect does an inhibitor have on a chemical reaction?

Increases the activation energy, slowing down the reaction Signup and view all the answers

In the equilibrium constant expression Kc = [NO]² · [O2] / [NO2]² for the reaction 2NO2 ⇌ 2NO + O2, what does a Kc value of 2.71 indicate?

The reaction favors the formation of products Signup and view all the answers

What defines the reaction rate in a chemical reaction?

The rate of change in concentration of reactants or products over time Signup and view all the answers

Which of the following factors is NOT a primary determinant of reaction rate?

Total volume of the reaction vessel Signup and view all the answers

In a second-order reaction, which of the following rate laws is applicable?

Rate = k[A]^2 Signup and view all the answers

What is the role of a catalyst in a chemical reaction?

To increase the reaction speed without being consumed Signup and view all the answers

How does an increase in temperature affect the reaction rate?

It increases the rate by providing more energy for molecular collisions Signup and view all the answers

What is activation energy (Ea) in the context of chemical reactions?

The minimum energy required to initiate a chemical reaction Signup and view all the answers

According to the Arrhenius equation, which factor does NOT directly affect the rate constant (k)?

Pressure of the surrounding environment Signup and view all the answers

What is the effect of increasing temperature on an endothermic reaction at equilibrium?

Equilibrium shifts in the forward direction Signup and view all the answers

Which statement correctly describes the role of a catalyst in a chemical reaction?

It lowers the activation energy and increases the rate of reaction. Signup and view all the answers

When Qc is less than Kc, what can be inferred about the reaction?

The reaction shifts to the right towards products. Signup and view all the answers

What happens to the equilibrium position when pressure is decreased in a reaction with gaseous products?

Equilibrium shifts to the side with more moles of gas. Signup and view all the answers

What does ΔH represent in a chemical reaction?

The enthalpy change during the reaction Signup and view all the answers

Which statement about Le Chatelier's principle is true?

Equilibrium shifts to minimize the effects of changes. Signup and view all the answers

What is the relationship between Kc and temperature for exothermic reactions when temperature is increased?

Kc decreases as temperature increases. Signup and view all the answers

Which of the following statements correctly defines a dynamic equilibrium?

Forward and reverse reactions occur at equal rates. Signup and view all the answers

How does removing a product from a reversible reaction at equilibrium affect Kc?

Kc does not change. Signup and view all the answers

Study Notes

Reaction Rates and Equilibrium

Reaction rate measures how quickly reactant concentrations change over time.
Reaction rate is expressed as [product]/time or -[reactant]/time
Rate law describes the relationship between reaction rate and reactant concentrations.
First-order reaction rate depends linearly on one reactant concentration.
Second-order reaction rate depends on the square of one reactant concentration or on the product of the concentrations of two reactants.
Zero-order reaction rate is independent of reactant concentration.
Factors affecting reaction rate:
- Concentration: Higher concentration generally leads to faster rates.
- Temperature: Higher temperatures increase reaction rates.
- Pressure (gases): Higher pressure generally increases reaction rates.
- Surface area (solids): Larger surface areas lead to faster rates.
- Catalysts: Catalysts speed up reactions by lowering activation energy without being consumed.
Activation energy (Ea): Minimum energy required to start a chemical reaction.

Chemical Equilibrium

Equilibrium is the state where the rates of forward and reverse reactions are equal.
Equilibrium constant (Kc): A constant that expresses the relationship between the concentrations of reactants and products at equilibrium.
Kc = [products]^coefficient / [reactants]^coefficient
Le Chatelier's Principle: If a system at equilibrium is perturbed (changed), the system will shift to counteract the change.

Equilibrium Shifts

Concentration changes: Adding reactants or removing products shifts equilibrium to favor product formation.
Temperature changes: Increasing the temperature favors the endothermic reaction; decreasing the temperature favors the exothermic reaction.
Pressure changes: Increasing pressure favors the side with fewer moles of gas.
Catalysts: Catalysts have no effect on the equilibrium position; they only affect the rate at which equilibrium is reached.

Reaction Quotient (Qc)

Reaction quotient (Qc): Similar to Kc, but calculated for any given set of concentrations, not just at equilibrium.
If Qc = Kc, the system is at equilibrium.
If Qc < Kc, the reaction will proceed to the right (toward products) to reach equilibrium.
If Qc > Kc, the reaction will proceed to the left (toward reactants) to reach equilibrium.

Catalysts

Heterogeneous catalysts: Catalysts in a different phase than the reactants.
Homogeneous catalysts: Catalysts in the same phase as the reactants.

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Description

This quiz covers the concepts of reaction rates, including factors that influence them, such as concentration, temperature, and pressure. Additionally, it explores the different types of reactions including first-order, second-order, and zero-order reactions. Test your understanding of how these elements interact in chemical reactions.