Which is the lightest element in the universe?

$\begin{array}{*{20}{c}}
{C{H_3}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C{H_3}\,\,\,\,\,\,\,\,\,\,}\\
{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}\\
{C{H_3} - C{H_2} - C = C - CH - C - C{H_2} - C{H_2} - C{H_3}}\\
{|\,\,\,\,\,\,\,\,\,}\\
{{C_2}{H_5}}
\end{array}$

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Among the following species, the diamagnetic molecule is

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The heat of hydrogenation for $3$ -methylbutene and $2$ -pentene are $-30\, kcal/mol$ and $-28\,kcal/mol$ respectively. The heats of combustion of $2$ -methylbutane and pentane are - $784 \,kcal / mol$ and $-782 \,kcal/mol$ respectively. All the values are given under standard conditions. Taking into account that combustion of both alkanes give the same products, what is $\Delta H$ (in $kcal/mol$) for the following reaction under same conditions ?

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The number of oxygen atoms in $4.4\ gm$ of $CO_2$ is approx.

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Spontaneity of a chemical reaction is decided by the negative change in

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Consider the following ionisation reactions

$I.E.\, (kJ \,mol^{-1})$	$I.E.\, (kJ\, mol^{-1})$
$A_{(g)} \to A^+_{(g)}+e^-,$ $A_1$	$B_{(g)} \to B^{+}_{(g)}+e^-,$ $B_1$
$B^+_{(g)} \to B^{2+}_{(g)}+e^-,$ $B_2$	$C_{(g)} \to C^{+}_{(g)}+e^-,$ $C_1$
$C^+_{(g)} \to C^{2+}_{(g)}+e^-,$ $C_2$	$C^{2+}_{(g)} \to C^{3+}_{(g)}+e^-,$ $C_3$

If monovalent positive ion of $A,$ divalent positive ion of $B$ and trivalent positive ion of $C$ have zero electron. Then incorrect order of corresponding $I.E.$ is

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Number of products

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Some Basic Concepts of Chemistry — Chemistry STD 11 Science — Question

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