One mole of an aldehyde $R-CHO$ reacts completely with dinitrophenylhydrazine to form one mole of a precipitate of dinitrophenylhydrazone:
$4.40\;g$ of an aldehyde ($R-CHO$) brought $22.4\;g$ of dinitrophenylhydrazone.
Search the condensed formula of this aldehyde!
Molecular formula of dinitrophenylhydrazone:
$C_7H_5N_4O_4R$
Let be x the mass of the R group:
$M_{hydrazone}$ $=$ $84$ $+$ $5$ $+$ $56$ $+$ $64$ $+$ $x$ $=$ $209$ $+$ $x$
Molecular formula of aldehyde $A$:
$CHOR$
$M_{A}$ $=$ $12+1+16+x$$=29+x$
$n_A$ $=$ $n_{hydrazone}$
$\frac{4.40}{29+x}$ $=$ $\frac{22.4}{209+x}$
$x=15$
$R=CH_3$
$A$ is ethanal
$CH_3CHO$
$4.40\;g$ of an aldehyde ($R-CHO$) brought $22.4\;g$ of dinitrophenylhydrazone.
Search the condensed formula of this aldehyde!
