Chemistry Module 5: Equilibrium and Reactions
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Questions and Answers

What is Le Chatelier's principle primarily concerned with?

  • The response of equilibrium to disturbances (correct)
  • The effect of temperature on reaction rates
  • The relationship between pressure and rate of reaction
  • The establishment of equilibrium in reaction systems

In static equilibrium, which of the following statements is true?

  • The system is continuously reacting
  • There is no conversion of reactants to products (correct)
  • Concentrations of reactants and products are changing constantly
  • The rates of forward and reverse reactions are at their maximum

What effect does increasing pressure have on a reaction where the number of gas particles is unequal?

  • The equilibrium shifts towards the side with more gas particles
  • The equilibrium position remains unchanged
  • It increases the rates of both forward and reverse reactions equally
  • The equilibrium shifts towards the side with fewer gas particles (correct)

Which of the following statements accurately describes an exothermic reaction?

<p>The reaction is spontaneous with ΔG &lt; 0 (A)</p> Signup and view all the answers

According to collision theory, how does a decrease in volume affect gas molecules?

<p>Gas molecules are closer, increasing collision frequency (A)</p> Signup and view all the answers

What is the effect of adding an inert gas to a system at equilibrium?

<p>It raises total pressure without changing concentrations (C)</p> Signup and view all the answers

In a system where reactants and products have equal moles, how does changing pressure affect the equilibrium?

<p>There is no shift in equilibrium position (A)</p> Signup and view all the answers

What happens to entropy during photosynthesis?

<p>Entropy decreases because the process is endothermic (A)</p> Signup and view all the answers

What is the effect of adding water to a reaction at equilibrium?

<p>It decreases the concentration of both products and reactants. (C)</p> Signup and view all the answers

How does temperature affect an exothermic reaction at equilibrium?

<p>Increasing temperature favors the reverse reaction. (C)</p> Signup and view all the answers

What role does a catalyst play in a chemical reaction?

<p>It lowers the activation energy for both reactions. (D)</p> Signup and view all the answers

In a system where Q < Keq, what is the expected change in equilibrium position?

<p>The reaction will shift to the right to form more products. (D)</p> Signup and view all the answers

How is the equilibrium constant (Keq) calculated in a reaction?

<p>It is the concentrations of products divided by the concentrations of reactants. (A)</p> Signup and view all the answers

Which statement best describes collision theory?

<p>Reactions occur when particles collide with sufficient energy. (D)</p> Signup and view all the answers

What is the effect of an increase in temperature on the rates of reactions at equilibrium?

<p>It increases the rates of both forward and reverse reactions equally. (D)</p> Signup and view all the answers

What happens to the reaction quotient (Q) when more reactants are added to a system at equilibrium?

<p>Q increases and the system shifts left. (A)</p> Signup and view all the answers

Which condition indicates a spontaneous reaction based on Gibbs free energy?

<p>∆G &lt; 0 (C)</p> Signup and view all the answers

What characterizes a dynamic equilibrium?

<p>The rate of the forward reaction equals the rate of the reverse reaction (D)</p> Signup and view all the answers

Which of the following is true regarding an endothermic forward reaction?

<p>It absorbs energy (C)</p> Signup and view all the answers

What effect does increasing the concentration of reactants have on a system at equilibrium?

<p>It shifts equilibrium toward the products (D)</p> Signup and view all the answers

What can be concluded about reactions that are classified as irreversible?

<p>They can only produce products (D)</p> Signup and view all the answers

Which of the following pairs are examples of reversible reactions?

<p>Formation of saturated sugar solution and evaporation (D)</p> Signup and view all the answers

When considering collision theory, which factor does not contribute to a successful collision?

<p>Dynamically stable reactants (B)</p> Signup and view all the answers

In a system where ∆H > 0 and ∆S < 0, what can be inferred about the reaction's spontaneity?

<p>The reaction is non-spontaneous (C)</p> Signup and view all the answers

The reaction between iron (III) nitrate and potassium thiocyanate produces a red complex. What does this indicate about the nature of the reaction?

<p>It reaches equilibrium (A)</p> Signup and view all the answers

What happens to the rate of reaction as the concentration of hydrogen and nitrogen decreases in the formation of ammonia?

<p>The rate of ammonia production decreases (C)</p> Signup and view all the answers

Flashcards

Collision Theory

Collisions with inert gases don't cause reactions.

Dilution Effect

Adding water lowers the concentration of reactants and products, shifting equilibrium to the side with more dissolved particles.

Temperature Effect (Exothermic)

Increasing temperature increases kinetic energy, favouring the reverse reaction in an exothermic reaction, as the reaction absorbs energy.

Temperature Effect (General)

Increasing temperature increases the rates of both forward and reverse reactions equally.

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Catalyst Effect

A catalyst lowers the activation energy for both forward and reverse reactions, speeding up both.

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Equilibrium Constant (Keq)

Keq is the ratio of product concentrations to reactant concentrations at equilibrium (aqueous and gases only).

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Equilibrium Shift (Q<Keq)

If Q (reaction quotient) is less than Keq, the reaction will shift to the right to form more products.

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Equilibrium Shift (Heterogeneous Reactions)

The concentration of pure solids or liquids is considered 1 when calculating equilibrium constants.

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Static Equilibrium

A state where the forward and reverse reaction rates are equal, resulting in no observable change in reactant or product concentrations.

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Dynamic Equilibrium

A state where the forward and reverse reactions occur at equal rates, with concentrations remaining constant as products are continuously formed and reactants continuously reformed in a reciprocal process.

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Le Chatelier's Principle

If a stress is applied to a system in equilibrium, the system will shift in a way that relieves the stress.

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Effect of Pressure/Volume on Equilibrium

An increase in pressure/decrease in volume shifts the equilibrium to the side with fewer gas moles. This is observed by the concentrations of each specie adjusting to accomodate the disturbance.

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Equilibrium Shift

The change in the relative concentrations of reactants and products in an equilibrium reaction when the conditions are changed.

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Spontaneous Reaction

A reaction that occurs naturally without external intervention. This includes reaction where the Gibbs Free Energy (ΔG) is negative

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Gibbs Free Energy (ΔG)

A thermodynamic potential that measures the maximum reversible work that may be performed by a thermodynamically closed system at a constant temperature and pressure.

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Factors Affecting Equilibrium

Equilibrium is affected by concentration, temperature, and pressure/volume of a system.

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Gibbs Free Energy

A thermodynamic quantity that determines the spontaneity of a reaction. A negative Gibbs free energy change (ΔG < 0) indicates a spontaneous reaction, while a positive change (ΔG > 0) indicates a non-spontaneous reaction. A zero change (ΔG = 0) signifies equilibrium.

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Non-Spontaneous Reactions

Reactions that require external energy input to occur. They have a positive Gibbs free energy change (ΔG > 0).

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Equilibrium

A state where the rates of the forward and reverse reactions are equal, leading to no net change in the concentrations of reactants and products.

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Closed System

A system that does not exchange matter with its surroundings, but can exchange energy. Reactions in closed systems can reach equilibrium.

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Reversible Reaction

A reaction where the products can react to re-form the original reactants. These reactions can reach equilibrium.

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Rate of Reaction

The speed at which a chemical reaction proceeds. It's affected by factors like concentration, temperature, and the presence of catalysts.

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Activation Energy

The minimum amount of energy required for reactant molecules to collide and react. This energy is needed to break existing bonds and form new ones.

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Study Notes

Periodic Table of Elements

  • A tabular arrangement of elements
  • Organized by atomic number
  • Elements are grouped by similar properties
  • Includes information such as atomic number, atomic mass, symbol, and name of each element

Working Scientifically

  • Observation: using senses and instruments
  • Hypothesis: a testable explanation
  • Method (Procedure): step-by-step description of the experiment
  • Validity: only one variable is changed at a time, testing the hypothesis
  • Reliability: repeated experiment with consistent results
  • Accuracy: correct measurements, reducing systematic errors
  • Precision: consistent measurements, reducing random errors

Module 5: Equilibrium and Acid Reactions

  • Static and dynamic equilibrium: in static equilibrium, reactions do not progress further; there is no change in concentrations. Dynamic equilibrium involves forward and reverse reactions occurring at equal rates; concentrations are constant
  • Gibbs free energy and chemical reactions: a decrease in Gibbs free energy (ΔG < 0) suggests a spontaneous reaction, while a positive value suggests a non-spontaneous one.
  • Open and closed systems: in open systems, both matter and energy can transfer, whereas, in closed systems, only energy transfer is possible

Reversible and Irreversible Systems

  • Irreversible: processes that cannot be reversed under normal conditions (e.g. combustion, neutralisation).
  • Reversible: processes that can be reversed by changing conditions (e.g. evaporation/condensation of water).

Experiments

  • Experiment 1: Reaction of hydrated cobalt (II) chloride and dehydrated cobalt (II) chloride; reversible reaction
  • Experiment 2: Reaction of iron (III) nitrate and potassium thiocyanate; reversible reaction; two solutions mixed to form a red substance

Collision Theory

  • Successful collisions: successful collisions require the correct orientation and sufficient kinetic energy.

Dynamic Equilibrium

  • Rate of the forward and reverse reactions are equal
  • The concentrations remain constant

Equilibrium Law

  • Equilibrium constant (Keq) is the ratio of the concentrations of products to reactants at equilibrium (only for gases and aqueous solutions)
  • Reactant and product concentrations raised to the power of the coefficients in the reaction equation

Heterogeneous reactions

  • The concentration of pure solid or liquid is 1 (omitted from the equilibrium reaction)

Solution Equilibria

  • Solubility rules: used to predict the solubility of ionic compounds in water.

Module 6: Acid/Base Reactions

  • Module about acid-base reactions.

Module 7: Organic Chemistry

  • Module about organic chemistry.

Module 8: Applying Chemical Ideas

  • Applying chemical concepts in various contexts, possibly more complicated examples or applications.

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Description

This quiz covers key concepts in chemistry, focusing on the periodic table of elements, scientific methodology, and the principles of equilibrium in chemical reactions. Evaluate your understanding of atomic properties, experimental procedures, and the dynamics of acid reactions. Test your knowledge and ensure you grasp these fundamental topics!

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