Please identify the limiting reactant of the following reactions:$-$

a$.PQ$

Feeds: $90\%$ inert and $10\%P$

b$.P+Q2R+S,$

Feeds: equal molar flow rate of $P$ and $Q$

c$.2P+Q\frac{1}{2}R+S,$

Feeds: equal molar flow rate of $P$ and $Q$

d$.P+QR+2S,$

Feeds: $80\%$ inert, $10\%P$ and $10\%$ Q

e$.P+\frac{1}{2}QR$

Feeds: $25\%$ P and $75\%$ Q

f$.P+2QR+2S$

Feeds: equal number of mole of $P$ and $Q$

g$.P+QR$

Feeds: ratio between $P$ and $Q$ is $3$:$1$