Question

State which one is homogeneous or heterogeneous?
(a) $C_{Diamond}\rightleftharpoons C_{graphite}$

(b) $H_2{O}_{\left(s\right)}\rightleftharpoons H_2{O}_{\left(l\right)}$

(c) $N_{2\left(g\right)}+3H_{2\left(g\right)}\rightleftharpoons 2N{H}_{3\left(g\right)}$

(d) $MgC{O}_{3\left(s\right)}\rightleftharpoons Mg{O}_{\left(s\right)}+C{O}_{2\left(g\right)}$

(e) $PC{l}_{3\left(g\right)}+C{l}_{2\left(g\right)}\rightleftharpoons PC{l}_{5\left(g\right)}$.

Answer 1

Homogeneous systems have phase $\left(P\right)=1$
A system with $P\ge 2$ is called heterogeneous.
Phases in a system can be determined by following the rules given below.

System	Phase $\left(P\right)$	Explanation
$S+S$	$2$	No. of solid in mixture give number of phase $=2$ i.e. $P=2$
$S+L$	$1$	Soluble systems lead to $P=1$
$S+L$	$2$	Insoluble systems lead to $P=2$
$L+L$	$2$	Immiscible liquids lead to $P=2$
$L+L$	$1$	Miscible liquids lead to $P=1$
$G+G$	$1$	All gases in a mixture give $P=1$

Thus given system	$a$	$b$	$c$	$d$	$e$
Number of phase	$2$	$2$	$1$	$3$	$1$

$\therefore$ (c) and (e) are Homogeneous systems.

(a), (b) and (d) are Heterogeneous systems.