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Questions and Answers
What does the Wurtz Fitting Reaction involve?
A reaction between an alkyl halide and aryl halide with sodium metal in dry ether.
Which type of reaction occurs at a very fast rate and cannot be measured by normal methods?
What is the rate of a chemical reaction?
The change in concentration of a reactant or product per unit time.
The average rate of a reaction can be calculated as [Change in concentration of reactant or product]/[____].
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The rate should always be negative because reactants decrease with time.
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What does the term 'activation energy' refer to?
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What is a catalyst?
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What happens to the rate of reactions as temperature increases?
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Study Notes
Chemical Kinetics
- Definition: The study of the rates and mechanisms of chemical reactions
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Categorizing Reactions by Rate:
- Instantaneous Reactions (Fast): occur rapidly, rate immeasurable by conventional methods, usually ionic reactions
- Examples: Acid-Base Reactions, precipitation reactions like NaCl + AgNO3
- Very Slow Reactions: take years to complete, rates immeasurable
- Examples: Rusting of Iron, graphite to diamond conversion
- Moderately Slow Reactions: take a definite time to complete, rates measurable
- Example: CH3-S-CH3(aq) + H-O-O2S(aq) -> CH3-S-O2HS(aq) + H2O
Rate of a Chemical Reaction
- Definition: Change in concentration of reactant or product per unit time
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Formula: Rate (r) = - (ΔR/Δt) = + (ΔP/Δt)
- Negative sign for reactants (concentration decreases)
- Positive sign for products (concentration increases)
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Average Rate:
- Change in molar concentration over a given time interval
- Formula: Average Rate = [Change in concentration]/[Time interval]
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Instantaneous Rate:
- Rate at a specific instant in time
- Represented as the slope of the tangent at a point on the concentration-time curve
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Average Rate of Reaction:
- Represented as the slope of the secant between two points on the concentration-time curve
Rate of Disappearance of a Reactant
- Definition: Ratio of change in reactant concentration over time
- Formula: V = - (ΔC/Δt)
- Note: Rate is always positive, even though the change in concentration is negative
Rate of Formation of a Product
- Definition: Ratio of change in product concentration over time
- Formula: V = (ΔC/Δt)
Factors Affecting Rate
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State of Matter: Gaseous reactants are most reactive, followed by liquids, then solids
- Reasons: More collisions in a gas, larger surface area in liquids compared to solids
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Collision of Reactants:
- Necessary for a reaction to proceed
- Must have sufficient energy (activation energy)
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Temperature: Increased temperature typically leads to an increased rate of reaction
- Activation Energy (Ea): Minimum energy required to start a reaction
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Catalyst:
- Alters reaction rate without being consumed
- Lowers activation energy, increasing reaction rate
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Description
This quiz covers the fundamental concepts of chemical kinetics, including definitions, categorization of reactions by rate, and the mathematical formulation of reaction rates. Explore instantaneous, slow, and moderately slow reactions, along with examples for each type. Test your understanding of how reaction rates are measured and the significance of concentration changes over time.
