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Q.
Among $NH_{3}, HNO_{3}, NaN_{3}$ and $Mg_{3}N_{2}$. Find the number of molecules having nitrogen in negative oxidation state
Redox Reactions
Solution:
Calculating the oxidation state of nitrogen in given molecules;
Oxidation state of $N$ in $NH_{3}$ is
$x+3 \times (+1)=0$ or $x=-3$
Oxidation state on $N$ in $NaNO_{3}$ is
$1+x+3 \times (-2)=0$ or $x=+5$
Oxidation state of $N$ in $NaN_{3}$ is
$+1+3x=0$ or $x=-\frac{1}{3}$
Oxidation state of N in $Mg_{3}N_{2}$ is
$3 \times 2 +2x=0$ or $x=-3$
Thus 3 molecules (i.e. $NH_{3}, NaN_{3}$ and $Mg_{3}N_{2}$, have nitrogen in negative oxidation state