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CUET · CHEMISTRY · PYQ PAPER 2025

Read the passage carefully and answer the questions based on the passage:
The number of reacting species (atoms, ions or molecules) taking part in an elementary reaction, which must collide simultaneously in order to bring about a chemical reaction is called molecularity of a reaction. In the rate equation Rate \(=k[\mathrm{~A}]^x[\mathrm{~B}]^y\)
\(x\) and \(y\) indicate how sensitive the rate is to the change in concentration of A and B, respectively. Sum of these exponents, i.e., \(x +y\) gives the overall order of a reaction where \(x\) and \(y\) represent the order with respect to the reactants A and B respectively. Hence, the sum of powers of the concentration of the reactants in the rate law expression is called the order of that chemical reaction. For a first order reaction, the concentration of the reactant varies as \([\mathrm{R}]=[\mathrm{R}]_0 e^{-k t}\)
The units of first and zero order rate constant of reactions are respectively:

  1. A \(s^{-1}, M s^{-1}\)
  2. B \(M s^{-1}, s^{-1}\)
  3. C \(M, s^{-1}\)
  4. D \(s^{-1}, M\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(M, s^{-1}\)

Step-by-step Solution

Detailed explanation

For a first order reaction, rate \(= k[\mathrm{R}]\) \(M s^{-1} = k \cdot M \Rightarrow k = s^{-1}\) For a zero order reaction, rate \(= k[\mathrm{R}]^0 = k\) \(k = M s^{-1}\)
From CUET
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