Chemistry: Rates of Reactions and Reversible Reactions
Rates of Reaction
Reaction speed measured by changes in reactants and products on a graph.
Steeper the line, faster the reaction; less steep indicates slower reaction.
Factors Affecting Reaction Rate
Temperature: Higher temperature increases particle energy, resulting in more successful collisions.
Concentration/Pressure: Higher concentration leads to more particles in a volume, increasing collision frequency.
Surface Area: More exposed surface area promotes more collisions.
Catalysts: Substances that lower activation energy, enhancing reaction rate without being consumed.
Measurement of Reaction Rate
Three methods to measure:
Color change observation.
Change in mass (usually for gases).
Volume of gas produced (measured using gas syringe).
Experiment on Concentration Effects
Sodium Thiosulfate & HCl:
Prepare solutions and observe the time until the cross disappears.
Experiment with varying concentrations.
Magnesium & HCl:
Set up with gas syringe to measure gas volume produced over time.
Reaction Rate Graphs
Graph depicts product formation and reactant usage over time (y-axis vs. x-axis).
Mean rate calculated using overall change in y-value over time.
Tangents can be drawn to find instantaneous rates at specific points on the graph.
Reversible Reactions and Equilibrium
General form: A + BC ⇌ D
Equilibrium achieved only in a closed system; products and reactants are equal.
Dynamic equilibrium occurs with forward and reverse reactions happening simultaneously.
Le Chatelier's Principle: If conditions are changed at equilibrium, the system will shift to oppose that change.
Temperature shift: Endothermic or exothermic reactions will prevail based on the direction of the shift.
Pressure shift: Movement to the side with fewer molecules or vice versa. /