The decrease in atomic volume from Cr to Cu is very negligible be…

$H - H$ bond energy	$:\, 431.37 \,kJ\, mol^{-1}$
$C= C$ bond energy	$:\, 606.10\, kJ \,mol^{-1}$
$C - C$ bond energy	$:\, 336.49\, kJ\, mol^{-1}$
$C - H$ bond energy	$:\, 410.50\, kJ\, mol^{-1}$

Enthalpy for the reaction,

$\begin{array}{*{20}{c}}
{H\,\,\,\,H} \\
{|\,\,\,\,\,\,\,\,|} \\
{C = C} \\
{|\,\,\,\,\,\,\,\,\,|} \\
{H\,\,\,\,H}
\end{array}\, + \,H - H\, \to \,\begin{array}{*{20}{c}}
{H\,\,\,\,H} \\
{|\,\,\,\,\,\,\,\,|} \\
{H - C - C - H} \\
{|\,\,\,\,\,\,\,\,\,|} \\
{H\,\,\,\,H}
\end{array}\,$

will be .............. $\mathrm{kJ \,mol}^{-1}$

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For $n^{th}$ order reaction where $(n < 1)$

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Which isomer of cyclohexane hexachloride is a very strong insecticide

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For a reaction $A \to B$, the rate of reaction quadrupled when the concentration of $A$ is doubled. The rate expression of the reaction is $r = K{(A)^n}$. when the value of $n$ is

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Fuel cell, using hydrogen and oxygen as fuels,

$A$. has been used in spaceship

$B$. has as efficiency of $40 \%$ to produce electricity

$C$. uses aluminium as catalysts