Chemistry: Equilibrium and Chemical Equations
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Questions and Answers

Which of the following describes an open system?

  • Both mass and energy can be exchanged with the surroundings. (correct)
  • Only energy can be exchanged with the surroundings.
  • Mass and energy cannot be exchanged with the surroundings.
  • Only mass can be exchanged with the surroundings.

    • In a closed system, both mass and energy can be exchanged with the surroundings.

    False

    What does Le Chatelier’s principle state about a system at equilibrium?

    It will move in the opposite direction to undo changes and relieve imposed stresses.

    An insulated thermos bottle is an example of an ______ system.

    <p>isolated</p> Signup and view all the answers

    Match the following types of systems with their characteristics:

    <p>Open System = Both mass and energy can be exchanged Closed System = Energy exchanged, mass remains constant Isolated System = Neither mass nor energy can be exchanged</p> Signup and view all the answers

    What will happen if the concentration of a reactant in an equilibrium reaction is increased?

    <p>The reaction will shift right.</p> Signup and view all the answers

    Adding a catalyst affects the position of equilibrium in a reaction.

    <p>False</p> Signup and view all the answers

    What effect does increasing the volume of a reaction mixture have on the equilibrium?

    <p>It shifts the reaction left.</p> Signup and view all the answers

    Which of the following statements best describes an endothermic reaction?

    <p>Heat is absorbed from the surroundings.</p> Signup and view all the answers

    Exothermic reactions absorb energy from their surroundings.

    <p>False</p> Signup and view all the answers

    What is the chemical formula for sodium chloride produced from the reaction of sodium hydroxide and hydrochloric acid?

    <p>NaCl</p> Signup and view all the answers

    Indicators like blue litmus paper turn _____ in acidic solutions.

    <p>red</p> Signup and view all the answers

    Match the acid or base with its strength:

    <p>Hydrochloric acid = Strong acid Acetic acid = Weak acid Sodium hydroxide = Strong base Ammonium hydroxide = Weak base</p> Signup and view all the answers

    Which acid-base reaction represents a weak acid reacting with a strong base?

    <p>CH3COOH + NaOH → CH3COONa + H2O</p> Signup and view all the answers

    A concentrated solution has more molecules of solute than a dilute solution.

    <p>True</p> Signup and view all the answers

    What color does red litmus paper turn in an alkaline solution?

    <p>blue</p> Signup and view all the answers

    What does the symbol '⇌' signify in a chemical reaction?

    <p>The reaction can proceed in both directions</p> Signup and view all the answers

    If more products are present in a reaction, the equilibrium position will shift to the left.

    <p>False</p> Signup and view all the answers

    What happens to the rate of the forward and backward reactions as equilibrium is reached?

    <p>They become equal.</p> Signup and view all the answers

    An _____ system can exchange both matter and energy with its surroundings.

    <p>open</p> Signup and view all the answers

    Match the following types of systems with their definitions:

    <p>Open System = Exchanges both matter and energy Closed System = Exchanges energy but not matter Isolated System = Does not exchange matter or energy Equilibrium = Rates of forward and backward reactions are equal</p> Signup and view all the answers

    What effect does adding heat to a reaction at equilibrium typically have?

    <p>Encourages the forward reaction</p> Signup and view all the answers

    Equilibrium can only be reached if the reaction occurs in an open system.

    <p>False</p> Signup and view all the answers

    What happens to the backward reaction as the concentration of products increases?

    <p>It speeds up.</p> Signup and view all the answers

    When there are more reactants in a reaction, the equilibrium shifts to the _____ side.

    <p>left</p> Signup and view all the answers

    Which of the following is true about equilibrium?

    <p>The position can change based on conditions</p> Signup and view all the answers

    Study Notes

    Equilibrium

    • Equilibrium is reached when the rates of the forward and reverse reactions are equal, resulting in no net change in concentrations of reactants and products.
    • The symbol "⇌" indicates a reversible reaction.
    • Initially, the forward reaction is faster, but as reactants are consumed, it slows down, while the reverse reaction speeds up.
    • Equilibrium can be shifted left or right depending on changes in concentration, pressure, volume, or temperature.
    • Increasing product concentration shifts equilibrium to the left, while increasing reactant concentration shifts it to the right.
    • Equilibrium can only be achieved in a closed system where no reactants or products can escape.

    Writing and Balancing Chemical Equations

    • Common Polyatomic Ions:
      • Ammonium: NH4+
      • Acetate: C2H3O2−
      • Bicarbonate (Hydrogen Carbonate): HCO3−
      • Bisulfate (Hydrogen Sulfate): HSO4−
      • Carbonate: CO32-
      • Chromate: CrO42−
      • Cyanide: CN−
      • Dichromate: Cr2O72−
      • Hydroxide: OH−
      • Nitrate: NO3−
      • Nitrite: NO2−
      • Peroxide: O22−
      • Permanganate: MnO4−
      • Phosphate: PO43−
      • Sulfate: SO42−
      • Sulfite: SO32−
      • Thiocyanate: SCN−
      • Hypochlorite: ClO−
      • Chlorite: ClO2−
      • Chlorate: ClO3−
      • Perchlorate: ClO4−
      • Hydrogen Phosphate: HPO42−
      • Dihydrogen Phosphate: H2PO4−
      • Hydrogen Sulfide: HS−
      • Oxalate: C2O42−

    Open, Closed & Isolated Systems

    • Open System: Exchanges both matter and energy with its surroundings. Examples: an open flask, a boiling pot of water, and a living organism.
    • Closed System: Exchanges energy but not matter with its surroundings. Examples: a sealed container, a pressure cooker, and a greenhouse.
    • Isolated System: Cannot exchange matter or energy with its surroundings. Examples: an insulated thermos bottle, and the universe (theoretically).

    Le Chatelier’s Principle

    • Le Chatelier's principle states that if a change in conditions is applied to a system at equilibrium, the system will shift in a direction that relieves the stress.
    • Increasing the concentration of a reactant shifts the reaction to the right (towards products), while increasing the concentration of a product shifts it to the left (towards reactants).
    • Increasing volume shifts the reaction left (towards reactants), while decreasing volume shifts it right (towards products) to increase total pressure on the side with more moles of gas.
    • Adding a catalyst does not affect equilibrium position, as it speeds up both the forward and reverse reactions equally.
    • Increasing the partial pressure of a reactant shifts the reaction to the right, while increasing the partial pressure of a product shifts it to the left.

    Endothermic and Exothermic Reactions

    • Endothermic Reactions: Absorb heat from the surroundings.
    • Exothermic Reactions: Release heat to the surroundings.

    Acid-Base Reactions

    • Some common Acid-Base Reactions:
      • NaOH + HCl → NaCl + H2O (Acid + Base)
      • NH4OH + HCl → NH4Cl + H2O (Strong acid + weak base)
      • CH3COOH + NaOH → CH3COONa + H2O (Weak acid + strong base)
      • CH3COOH + NH4OH → CH3COONH4 + H2O (Weak acid + Weak base)
      • NaHCO3 + HCl → NaCl + H2O + CO2 (Metal Carbonate + Strong acid)
      • Ca(OH)2 + CO2 → CaCO3 + H2O (Non-metallic oxide with base)

    Strength vs Concentration and Equilibrium

    • Strength of an acid (or base): Refers to its ability to dissociate (ionize) in solution. Strong acids/bases dissociate completely, while weak acids/bases only partially dissociate.
    • Concentration of an acid (or base): Refers to the amount of acid or base dissolved in a given volume of solution. Higher concentration means more dissolved acid or base per unit volume.

    Indicators

    • Blue Litmus paper: Turns red in acidic solution.
    • Red Litmus paper: Turns blue in alkaline solution.
    • Universal Indicator: Provides a comprehensive pH measurement across the entire 0-14 scale, displaying a rainbow-like color spectrum for easy identification of acidity or alkalinity levels.
    • Litmus paper: A simple binary acid-base test using two colors, red and blue.

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    Chemistry Notes - Term 1 PDF

    Description

    Explore key concepts of chemical equilibrium and learn how to write and balance chemical equations in this engaging quiz. Understand the role of concentrations and the behavior of various polyatomic ions in chemical reactions. Test your knowledge on when and how equilibrium shifts in response to changes in conditions.

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