Chapter 6, Problem 6B.4E

Interpretation Introduction

Interpretation:

The rate constant for a gas-phase reaction was reported as $6.2\times {10}^{-14}c{m}^{-3}molecule{s}^{-1}{s}^{-1}$ at $298K$, this value has to be expressed in $d{m}^{3}mo{l}^{-1}{s}^{-1}$

Concept Introduction:

Rate of a reaction: It represents the speed at which a chemical reaction runs.  How much concentration of substrates (reactants) consumed and how much concentration of targets (products) formed in a unit of time is said to be rate of reaction.

For a general reaction,

$aA+bB\to cC+dD$

$\text{Rate}\text{=}\text{-}\frac{\text{1}}{\text{a}}\frac{\text{Δ}\left[\text{A}\right]}{\text{Δt}}\text{=}\text{-}\frac{\text{1}}{\text{b}}\frac{\text{Δ}\left[\text{B}\right]}{\text{Δt}}\text{=}\frac{\text{1}}{\text{c}}\frac{\text{Δ}\left[\text{C}\right]}{\text{Δt}}\text{=}\frac{\text{1}}{\text{d}}\frac{\text{Δ}\left[\text{D}\right]}{\text{Δt}}$

The negative sign indicates the reduction of concentration of reactant.

$\Delta \left[A\right],\Delta \left[B\right],\Delta \left[C\right]and\Delta \left[D\right]$ are the change in concentration of A,B, C and D over time period $\Delta t$

Avogadro number A mole is the number of atoms (or) molecules in $(1\text{g})$ of hydrogen or $12\text{g}$ of carbon. The number $6\times {10}^{23}$ is called one mole.

• From its given mass is,

  $\text{Number of moles}\text{=}\frac{\text{Given}\text{mass}}{\text{Molecular}\text{mass}}$

• From its given number of molecules is,

  $\text{Number of moles}\text{=}\frac{\text{number of molecules}}{\text{6}\text{.022}\text{×}{\text{10}}^{\text{23}}\text{molecules}}$