Question

A sample of $NaCl{O_3}$ is converted by heat to $NaCl$ with a loss of $0.16g$ of oxygen. The residue is dissolved in water and precipitated as $AgCl$. The mass of $AgCl\left( {in{\text{ }}g} \right)$ obtained will be: (Given: Molar mass of $AgCl = 143.5gmo{l^{ - 1}}$).
A. $0.41$
B. $0.35$
C. $0.48$
D. $0.54$

Answer 1

The first part of the reaction is a decomposition reaction of an inorganic salt. The precipitated residue undergoes a displacement reaction to produce a precipitated salt.

Complete step by step answer: The given reaction is the decomposition reaction of sodium chlorate under heating condition. The products of the reaction are $NaCl$ and oxygen. The reaction is
$NaCl{O_3} \to NaCl + {O_2}$
The balanced chemical equation is written as below:
$2NaCl{O_3} \to 2NaCl + 3{O_2}$
The balanced reaction indicates that $2moles$ of $NaCl{O_3}$ produces $2moles$ of $NaCl$ and $3moles$ of oxygen. The molar mass of ${O_2}$ molecule =$32\;g/mol$. Thus the moles of oxygen in $0.16g$ of oxygen is
=$0.16/32 = 0.005mol$.
The moles of $NaCl$ = $moles{\text{ }}of{\text{ }}oxygen \times \;\dfrac{{2{\text{ }}moles{\text{ }}NaCl}}{{3{\text{ }}moles{\text{ }}{O_2}}}$
=$0.005 \times \dfrac{2}{3} = 0.0033moles$
The $NaCl$ residue on dissolution in water gives $N{a^ + }$ ion and $C{l^ - }$ ion. $NaCl\left( {aq} \right) \to N{a^ + }(aq) + C{l^ - }(aq)$.
The aqueous solution on treatment with $AgN{O_3}$ undergoes a double displacement reaction to produce $NaN{O_3}$ and$AgCl$. The reaction is written as
$NaCl(aq) + AgN{O_3}(aq) \to NaN{O_3}(aq) + AgCl(s)$
The equation represents that the solution contains an equimolar mixture of $NaCl$ and $AgCl$. Thus the $0.0033moles$ $NaCl$ on precipitation will generate $0.0033moles$ of $AgCl$. The molar mass of $AgCl$ is$143.5gmo{l^{ - 1}}$.
Hence the mass of $AgCl\left( {in{\text{ }}g} \right)$obtained is
=$0.0033 \times 143.5 = 0.48g$.
Thus option C is the correct answer.

Note:
A mole of a substance is the ratio amount of the substance and the molar mass of that substance. It is equivalent to $6.023 \times {10^{23}}$ numbers of particles present in the substance. A displacement reaction is a type of chemical reaction in which displacement of a less reactive species occurs by a more reactive species. It seems to be an exchange of cations and anions from two substrates to products.