16.2.1 Calculating Rate Constants

Cards (40)

  • What does the rate constant (kk) quantify in a chemical reaction?

    Reaction speed
  • The rate constant (kk) changes with the concentration of reactants.

    False
  • The units of kk depend on the overall reaction order
  • Match the reaction order with the correct units of kk:

    0 ↔️ mol dm−3 s−1\text{mol} \, \text{dm}^{ - 3} \, \text{s}^{ - 1}
    1 ↔️ s−1\text{s}^{ - 1}
    2 ↔️ mol−1 dm3 s−1\text{mol}^{ - 1} \, \text{dm}^{3} \, \text{s}^{ - 1}
    3 ↔️ mol−2 dm6 s−1\text{mol}^{ - 2} \, \text{dm}^{6} \, \text{s}^{ - 1}
  • What does a higher value of kk indicate about a reaction?

    Faster reaction
  • If k=k =0.05 mol−1 dm3 s−1 0.05 \text{ mol}^{ - 1} \text{ dm}^{3} \text{ s}^{ - 1} for the reaction A+A +B→C B \to C, the reaction proceeds at a moderate speed
  • What does the rate law equation express?
    Reaction dependence on concentrations
  • The overall reaction order is determined theoretically.
    False
  • In the reaction 2NO(g)+2NO(g) +O2(g)→2NO2(g) O_{2}(g) \rightarrow 2NO_{2}(g), the rate law is Rate = k[NO]^{2}[O_{2}]</latex>, so the reaction is third order overall
  • How is the reaction order identified from the rate law?
    Sum the exponents
  • For the rate law Rate=Rate =k[NO]2[O2] k[NO]^{2}[O_{2}], the order with respect to NONO is 2
  • The overall reaction order is the sum of individual reaction orders.
  • What remains constant for a specific reaction at a given temperature?
    Rate constant
  • What determines the units of the rate constant kk?

    Reaction order
  • The rate constant kk relates the rate of a reaction to the concentrations of reactants in the rate law.
  • What are the units of kk for a zero-order reaction?

    mol dm−3 s−1\text{mol} \, \text{dm}^{ - 3} \, \text{s}^{ - 1}
  • A higher value of kk indicates a faster reaction.
  • For the reaction A+A +B→C B \to C, what is the value of kk if the rate law is \text{Rate} = k[A][B]</latex>?

    0.05 mol−1 dm3 s−10.05 \, \text{mol}^{ - 1} \, \text{dm}^{3} \, \text{s}^{ - 1}
  • What does the overall reaction order represent in the rate law equation?
    Sum of individual orders
  • For the reaction 2NO(g) + O_{2}(g) \rightarrow 2NO_{2}(g)</latex>, the overall reaction order is three.
  • How do you identify the reaction order from the rate law?
    Sum the exponents
  • In the rate law Rate=Rate =k[NO]2[O2] k[NO]^{2}[O_{2}], the reaction is second order with respect to O2O_{2}.

    False
  • What method is used to experimentally determine the rate constant kk?

    Initial rates method
  • Steps to calculate kk using initial rates data

    1️⃣ Identify a rate law
    2️⃣ Find two experiments where only one reactant concentration changes
    3️⃣ Use data to find mm and nn
    4️⃣ Substitute values into the rate law
    5️⃣ State the rate constant with units
  • To find the reaction order, compare two experiments where only one reactant concentration changes.
  • What formula is used to calculate kk once the reaction orders are known?

    k = \frac{Rate}{[A]^{m}[B]^{n}}</latex>
  • The reaction order with respect to reactant A in the example is 2.
  • What is the reaction order with respect to reactant B in the example?
    1
  • What method is used to determine the rate constant experimentally?
    Initial rates method
  • The initial rates method is used to calculate the rate constant.
  • Steps to calculate the rate constant using initial rates data
    1️⃣ Identify a rate law
    2️⃣ Find two experiments where only one reactant concentration changes
    3️⃣ Use data to find mm and nn
    4️⃣ Substitute values into the rate law to calculate kk
    5️⃣ State the rate constant value with its units
  • To find reaction orders, you compare experiments where only one reactant concentration changes
  • What formula is used to calculate the rate constant kk?

    k = \frac{Rate}{[A]^{m}[B]^{n}}</latex>
  • The rate constant must always include its correct units.
  • The order with respect to reactant B in the example is 1
  • What is the value of the rate constant kk in the example?

    20 mol−2dm6s−1\text{mol}^{ - 2} \text{dm}^{6} \text{s}^{ - 1}
  • Steps to solve rate constant problems using the initial rates method
    1️⃣ Identify the rate law
    2️⃣ Calculate reaction orders
    3️⃣ Determine the rate constant kk
    4️⃣ Include units
  • To calculate reaction orders, use the formula \frac{Rate_{2}}{Rate_{1}} = \left(\frac{[A]_{2}}{[A]_{1}}\right)^{m}</latex> where mm represents the order.
  • The order with respect to reactant A in the example is 2
  • What are the units of the rate constant kk in the example?

    mol−2dm6s−1\text{mol}^{ - 2} \text{dm}^{6} \text{s}^{ - 1}