Chemical Kinetics Flashcards for NEET — 20 cards

First 8 of 20 Chemical Kinetics flashcards

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1. Card 1 of 20

   For the reaction $aA + bB \rightarrow cC + dD$, write the expression for the average rate of reaction in terms of the reactants and products.

   Hint: Divide the rate of disappearance/appearance by the stoichiometric coefficient.

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   Answer

   Rate $= -\frac{1}{a}\frac{\Delta[A]}{\Delta t} = -\frac{1}{b}\frac{\Delta[B]}{\Delta t} = +\frac{1}{c}\frac{\Delta[C]}{\Delta t} = +\frac{1}{d}\frac{\Delta[D]}{\Delta t}$

2. Card 2 of 20

   State three key differences between the Order and Molecularity of a reaction.

   Hint: Molecularity is just the number of colliding molecules in one step.

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   Answer

   1. Order is determined experimentally; Molecularity is a theoretical concept. 2. Order can be zero, fractional, or an integer; Molecularity is always a positive integer (1, 2, 3). 3. Order applies to the overall reaction; Molecularity applies only to a single elementary step.

3. Card 3 of 20

   What is the general formula for the unit of the rate constant ($k$) for an $n^{th}$ order reaction?

   Hint: Plug in n=0 for zero order, n=1 for first order.

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   Answer

   Unit of $k = (\text{mol L}^{-1})^{1-n} \text{s}^{-1}$ OR $\text{mol}^{1-n} \text{L}^{n-1} \text{s}^{-1}$

4. Card 4 of 20

   What are the units of the rate constant ($k$) for Zero-order and First-order reactions?

   Hint: For 1st order, concentration terms cancel out.

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   Answer

   Zero-order: $\text{mol L}^{-1} \text{s}^{-1}$ (same as the rate of reaction) First-order: $\text{s}^{-1}$

5. Card 5 of 20

   Write the integrated rate equation for a Zero-order reaction.

   Hint: It resembles the equation of a straight line: y = mx + c

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   Answer

6. Card 6 of 20

   Write the integrated rate equation for a First-order reaction (in terms of log base 10).

   Hint: Use 2.303 to convert natural log (ln) to base 10 log.

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   Answer

   $k = \frac{2.303}{t} \log \frac{[A]_0}{[A]}$

7. Card 7 of 20

   For a first-order reaction, what is the slope of the graph when $\log[A]$ is plotted against time ($t$)?

   Hint: Because $\log[A] = \log[A]_0 - \frac{kt}{2.303}$

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   Answer

8. Card 8 of 20

   Write the formula for the Half-life ($t_{1/2}$) of a Zero-order reaction. How does it depend on initial concentration?

   Hint: More stuff takes longer to halve if the rate is constant.

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   Answer

   $t_{1/2} = \frac{[A]_0}{2k}$ It is directly proportional to the initial concentration ($[A]_0$).