Chemical Equilibrium and Reversible Reactions
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Questions and Answers

What happens to the rate of formation of substance B as the reaction progresses?

  • It varies randomly.
  • It increases from zero to a constant. (correct)
  • It remains constant.
  • It decreases to zero.

In the law of mass action, when is equilibrium reached?

  • When the concentrations of A and B are equal.
  • When the forward reaction rate exceeds the reverse reaction rate.
  • When the rate of formation of products equals the rate of formation of reactants. (correct)
  • When k[A] equals k[B].

Which is true regarding the equilibrium constant K?

  • It is influenced by the volume of the reaction vessel.
  • It has dimensions.
  • It must be specified with a balanced equation and temperature. (correct)
  • It includes concentrations of pure solids and liquids.

Which expression correctly represents the equilibrium constant for the reaction: aA + bB ⇋ cC + dD?

<p>K = [C]^c[D]^d/[A]^a[B]^b (C)</p> Signup and view all the answers

What is not included in the equilibrium constant expressions?

<p>Concentrations of pure solids. (A), Concentrations of solvents. (B), Concentrations of pure liquids. (C)</p> Signup and view all the answers

When balancing the reaction A + 2B ⇋ AB2, what do kf and kr represent?

<p>Rate constants for the forward and reverse reactions. (C)</p> Signup and view all the answers

For the reaction N2O4 (g) ⇋ 2NO2 (g), what does the equilibrium constant value of K = 4.63 x 10^-3 indicate?

<p>Reactants are favored at equilibrium. (D)</p> Signup and view all the answers

What defines a homogenous equilibrium?

<p>Reactions in which all reactants and products are in the same phase. (C)</p> Signup and view all the answers

What defines a state of chemical equilibrium?

<p>The rates of the forward and reverse reactions are equal. (B)</p> Signup and view all the answers

In a reversible reaction, what occurs as the reaction progresses towards equilibrium?

<p>Both forward and reverse reactions occur at varying rates before reaching equilibrium. (C)</p> Signup and view all the answers

What does a double arrow in a chemical equation signify?

<p>The reaction can proceed in both forward and reverse directions. (A)</p> Signup and view all the answers

Which statement is true about a reversible reaction at equilibrium?

<p>Reactant concentrations result in constant product concentrations. (D)</p> Signup and view all the answers

Which of the following best describes the effect of decreasing reactant concentration on a reversible reaction?

<p>The reverse reaction rate gradually increases. (A)</p> Signup and view all the answers

When equilibrium is achieved in a reversible reaction, what happens to the concentrations of reactants and products?

<p>Both reactants and products remain constant. (B)</p> Signup and view all the answers

Which best describes the dynamic nature of equilibrium in reversible reactions?

<p>Molecules of reactants and products continually interconvert. (C)</p> Signup and view all the answers

What happens to the rates of reactions as equilibrium is approached?

<p>The rates remain constant until both are equal. (D)</p> Signup and view all the answers

What is the value of $ abla n$ for the reaction $a A (g) + b B (g) \rightleftharpoons c C (g) + d D (g)$?

<p>c + d - a - b (A)</p> Signup and view all the answers

If $ abla n$ is negative for a reaction, what can be inferred about the relationship between the moles of gaseous products and gaseous reactants?

<p>There are more gaseous reactants than products. (D)</p> Signup and view all the answers

What would be the expression for $K_c$ given the reaction $2NO_2 (g) \rightleftharpoons 2NO (g) + O_2 (g)$?

<p>$K_c = \frac{[NO]^2}{[NO_2]^2}$ (C)</p> Signup and view all the answers

When converting $K_c$ to $K_p$, which of the following is correct?

<p>$K_p = K_c(RT)^{\nabla n}$ (D)</p> Signup and view all the answers

Using the equilibrium expression $K = \frac{[SO_3]}{[SO_2][O_2]^{1/2}}$, what is the balanced equation for the reaction?

<p>$SO_3(g) \rightleftharpoons SO_2(g) + \frac{1}{2}O_2(g)$ (D)</p> Signup and view all the answers

Given that $K_p = 158$ for the reaction $2NO_2 (g) \rightleftharpoons 2NO (g) + O_2 (g)$, calculate PO2 if PNO = 0.400 atm and PNO2 = 0.270 atm.

<p>72 atm (D)</p> Signup and view all the answers

What is the equilibrium constant $K_p$ for the reaction of ammonium hydrosulfide producing ammonia and hydrogen sulfide at 295 K?

<p>0.0702 (C)</p> Signup and view all the answers

For the mixture of SO2, O2, and SO3 reaching equilibrium at 852 K, what is the formula to calculate the equilibrium constant Kc?

<p>$K_c = \frac{[SO_3]}{[SO_2][O_2]}$ (D)</p> Signup and view all the answers

Flashcards

Chemical Equilibrium

A state where the rates of the forward and reverse reactions are equal, and the concentrations of reactants and products remain constant.

Reversible Reaction

A reaction where products can react to reform the original reactants.

Forward Reaction

The process of reactants turning into products in a chemical reaction.

Reverse Reaction

The process of products turning back into reactants in a chemical reaction.

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Equilibrium State

The point at which the rate of the forward reaction is equal to the rate of the reverse reaction, leading to constant concentrations of reactants and products.

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Rate of reaction

The speed at which a chemical reaction takes place.

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Concentration

The amount of a substance present in a given volume.

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Physical Equilibrium

A state of balance between two phases of matter (ex: a liquid and a gas).

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Equilibrium Constant (Kc)

A constant value that represents the ratio of product concentrations to reactant concentrations at equilibrium for a reversible reaction.

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Equilibrium

The state where the rates of the forward and reverse reactions are equal, and the concentrations of reactants and products remain constant.

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Law of Mass Action

The principle that at a given temperature, the ratio of product concentrations to reactant concentrations raised to their stoichiometric coefficients is constant.

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Equilibrium Expression

A mathematical expression that relates the concentrations of reactants and products in a balanced chemical equation to the equilibrium constant, Kc.

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Homogeneous Equilibrium

The equilibrium in which all reactants and products are in the same phase (e.g., all gases or all aqueous solutions).

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Velocity Constants (kf, kr)

Rate constants for the forward (kf) and reverse (kr) reactions in a reversible chemical reaction.

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Equilibrium Constant, Kc

Ratio of forward reaction rate constant (kf) over reverse reaction rate constant (kr), at equilibrium.

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Stoichiometric Coefficients

The numbers in front of the chemical formulas in a balanced chemical equation.

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Kp Calculation

Kp is the equilibrium constant expressed in partial pressures. It relates the partial pressures of products to reactants at equilibrium.

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Kp and Kc relationship

Kp and Kc are related by the equation Kp = Kc(RT)^Δn, where R is the ideal gas constant, T is the temperature in Kelvin, and Δn is the change in the number of moles of gas in the reaction.

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Δn Calculation

Δn (change in moles) is the difference between the moles of gaseous products and the moles of gaseous reactants in a balanced chemical equation.

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Equilibrium Constant expression

An equilibrium constant is a value that represents the ratio of products to reactants when the reaction system has reached equilibrium.

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Kc calculation

Kc is the equilibrium constant expressed in molar concentrations. It relates the concentrations of products to reactants at equilibrium.

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Partial Pressure

Partial pressure is the pressure exerted by a single gas in a mixture of gases.

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Balanced Chemical Reaction

A chemical equation that shows the correct number of moles of each substance involved in a reaction.

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Equilibrium Concentrations

The concentrations of reactants and products when the forward and reverse reaction rates are equal.

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Study Notes

Chemical Equilibrium

  • Equilibrium is a state where no observable changes occur over time.
  • Chemical equilibrium occurs when the rates of the forward and reverse reactions are equal.
  • Concentrations of reactants and products remain constant at equilibrium.
  • Physical equilibrium examples include liquid-vapor transitions.
  • Chemical equilibrium examples include reversible reactions like Nâ‚‚Oâ‚„ ↔ 2NOâ‚‚.

Reversible Reactions

  • Reversible reactions proceed in both forward and reverse directions.
  • At equilibrium, reactants and products coexist.
  • A double arrow indicates a reversible reaction (e.g., A + B ↔ C + D).
  • Examples of reversible processes include evaporation and condensation, liquid-vapor transitions, and some chemical reactions.

Law of Mass Action

  • Equilibrium expression describes the relationship between concentrations of products and reactants at equilibrium.
  • For a general reaction aA + bB ↔ cC + dD, the equilibrium expression is K = [C]c[D]d / [A]a[B]b
  • Equilibrium constant (K) is dimensionless.

Equilibrium Constant Expressions

  • Concentrations of reactants and products in the condensed phase are expressed in molarity (M).
  • Pure solids, liquids, and solvents are not included in the equilibrium expressions.
  • Equilibrium expressions must specify balanced equations and temperature.

Chemical Kinetics and Equilibrium

  • Equilibrium is reached when the rate of the forward reaction equals the rate of the reverse reaction.
  • The equilibrium constant is the ratio of the forward and reverse rate constants.
  • For the reaction A + 2B ↔ ABâ‚‚, K = [ABâ‚‚] / ([A][B]²)

Heterogeneous Equilibrium

  • Heterogeneous reactions involve reactants and products in different phases.
  • In heterogeneous equilibrium expressions, concentrations of pure solids and liquids are omitted.

Examples

  • Examples of acid rain production reactions are given, and the equilibrium constant is defined in relation to those reactions.
  • Equilibrium pressure calculations are shown for reactions.

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Related Documents

Chemical Equilibrium Lecture Notes PDF

Description

This quiz covers key concepts related to chemical equilibrium, including the definition of equilibrium, the nature of reversible reactions, and the law of mass action. Participants will explore how these concepts apply to both physical and chemical processes through various examples.

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