•Some chemical reactions are reversible under specific conditions. •Reversible reactions are represented with a double arrow (⇌). •Forward reactions convert reactants to products; reverse reactions do the opposite.

Open vs Closed Systems

•Open systems exchange matter with surroundings (e.g., evaporation in open glass). •Closed systems retain matter but allow energy transfer (e.g., heat). •Condensation in closed containers maintains dynamic equilibrium.

Reversibility in Changes

•Physical changes (e.g., melting, freezing) are typically reversible. •Chemical changes (e.g., combustion, rusting) are often irreversible. •Reversibility depends on whether the substance's composition is altered.

What is Dynamic Equilibrium?

•Reactions proceed both forwards and backwards at equilibrium • (⇌) •Weak acids partially dissociate in water •Occurs in closed systems with constant (but not equal) reactant/product concentrations

Reversibility Using Activation Energy

Both forward and reverse reactions require Eₐ

Factors Affecting Equilibrium

•Changes in shift equilibrium: –concentration –temperature –or pressure •Catalysts speed up both reactions without changing equilibrium position

Conditions for Reversibility

•Reactions must have enough energy to overcome activation energies in both directions. •Reaction proceeds readily in both directions. •Equilibrium is maintained. •Reaction is considered reversible.

Measuring Concentration via Spectroscopy

•Concentration of a substance can be measured using spectroscopy but only if the chemical of interest is the only one absorbing light of a particular wavelength •(UV-visible spectroscopy measures absorbance of light at specific wavelengths.)

Visual Indicators of Reaction Progress

•Colour of a solution can indicate the extent of some reactions. •This is especially true if one of the species is coloured. •Example: Iron(III) ions reacting with thiocyanate ions.

Interpreting Graph Shape

•Forward reaction rate decreases over time. •Reverse reaction rate increases over time.•Both curves meet and remain constant at equilibrium.

Concentration vs Time Graphs Overview

•Concentration is constant at equilibrium Eg. •H₂ and I₂ concentrations start high and ↓ over time. •HI concentration starts at 0 and ↑ until equilibrium is reached •If starting with HI, its concentration decreases while H₂ and I₂ increase

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chem U3 T1

chem unit 3

Question	Answer
Reversible Reactions	•Some chemical reactions are reversible under specific conditions. •Reversible reactions are represented with a double arrow (⇌). •Forward reactions convert reactants to products; reverse reactions do the opposite.
Open vs Closed Systems	•Open systems exchange matter with surroundings (e.g., evaporation in open glass). •Closed systems retain matter but allow energy transfer (e.g., heat). •Condensation in closed containers maintains dynamic equilibrium.
Reversibility in Changes	•Physical changes (e.g., melting, freezing) are typically reversible. •Chemical changes (e.g., combustion, rusting) are often irreversible. •Reversibility depends on whether the substance's composition is altered.
What is Dynamic Equilibrium?	•Reactions proceed both forwards and backwards at equilibrium • (⇌) •Weak acids partially dissociate in water •Occurs in closed systems with constant (but not equal) reactant/product concentrations
Reversibility Using Activation Energy	Both forward and reverse reactions require Eₐ
Factors Affecting Equilibrium	•Changes in shift equilibrium: –concentration –temperature –or pressure •Catalysts speed up both reactions without changing equilibrium position
Conditions for Reversibility	•Reactions must have enough energy to overcome activation energies in both directions. •Reaction proceeds readily in both directions. •Equilibrium is maintained. •Reaction is considered reversible.
Measuring Concentration via Spectroscopy	•Concentration of a substance can be measured using spectroscopy but only if the chemical of interest is the only one absorbing light of a particular wavelength •(UV-visible spectroscopy measures absorbance of light at specific wavelengths.)
Visual Indicators of Reaction Progress	•Colour of a solution can indicate the extent of some reactions. •This is especially true if one of the species is coloured. •Example: Iron(III) ions reacting with thiocyanate ions.
Interpreting Graph Shape	•Forward reaction rate decreases over time. •Reverse reaction rate increases over time.•Both curves meet and remain constant at equilibrium.
Concentration vs Time Graphs Overview	•Concentration is constant at equilibrium Eg. •H₂ and I₂ concentrations start high and ↓ over time. •HI concentration starts at 0 and ↑ until equilibrium is reached •If starting with HI, its concentration decreases while H₂ and I₂ increase

Created by: rad-r11

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