1) What quantity (moles) of hydrogen is produced per mole of $OH $ function reacting with excess sodium?
2) An aliphatic mono-alcohol $A$ has a mass density of $0.82 \frac{kg}{L}$ .
if $11.5\; mL$ of $A$ react with an excess of sodium, $1.40\; L\; H_2$ (STP) are collected.
Find the molecular formula of $A$ !
1)
One mole $OH$ provides one half-mole $H_2$
2)
$m_A$ $=$ $0.82\cdot 11.5$ $=$ $9.43\; g$
$n_{H_2}$ $=$ $\frac{1.40}{22.4}$ $=$ $0.0635\; mol$
2 mole $A$ give one mole $H_2$
$n_A$ $=$ $2\cdot 0.0635$ $=$ $0.127\; mol$
$M_A$ $=$ $\frac{m_A}{n_A}$ $=$ $74\; \frac{g}{mol}$
General formula of $A$:
$C_nH_{2n+2}O$
$12n$ $+$ $2n$ $+$ $2$ $+$ $16$ $=$ $74$
so: $n=4$
Molecular formula of $A$:
$C_4H_9OH$
