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PUCET (Punjab) Rate Constant — practice questions

Explore 5 free Rate Constant questions in PUCET (Punjab) Chemistry. Open each question or exercise to read its content, reference answers and available explanation.

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Rate Constant questions and exercises with answers

Showing questions 1–5 of 5.

The **rate constant** $k$ in a rate law equals the rate of reaction when:Read the answer and worked solution →For a zero-order reaction, the units of the rate constant $k$ are:Read the answer and worked solution →For a first-order reaction, the units of the rate constant $k$ are:Read the answer and worked solution →If rate = $k[A][B]^2$, what are the units of $k$?Read the answer and worked solution →For the reaction A + B → P with $\text{rate} = k[A][B]^2$, rate = $3.6 \times 10^{-2}$ mol dm⁻³ s⁻¹ when [A] = 0.2 M and [B] = 0.1 M. $k$ equals:Read the answer and worked solution →

Worked practice questions

The **rate constant** $k$ in a rate law equals the rate of reaction when:

  1. All reactant concentrations are zero
  2. All reactant concentrations are unity
  3. Temperature is zero kelvin
  4. Time is zero
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Correct answer: B. All reactant concentrations are unity

Putting unit concentrations into rate = $k[A]^x[B]^y$ gives rate = $k$. **So $k$ is the rate at unit concentrations of all reactants.**

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For a zero-order reaction, the units of the rate constant $k$ are:

  1. L mol⁻¹ s⁻¹
  2. mol L⁻¹ s⁻¹
  3. L² mol⁻² s⁻¹
  4. s⁻¹
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Correct answer: B. mol L⁻¹ s⁻¹

**Zero order:** rate = $k$ (independent of [A]). **So $k$ has the same units as rate: mol L⁻¹ s⁻¹.**

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For a first-order reaction, the units of the rate constant $k$ are:

  1. L² mol⁻² s⁻¹
  2. s⁻¹
  3. mol L⁻¹ s⁻¹
  4. L mol⁻¹ s⁻¹
Show answer and solution

Correct answer: B. s⁻¹

**First order:** rate = $k[A]$. Solving for $k$ units: (mol L⁻¹ s⁻¹)/(mol L⁻¹) = s⁻¹.

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