Question
An organic compound contains $$69\% $$ carbon and $$4.8\% $$ hydrogen, the remainder being oxygen. What will be the masses of carbon dioxide and water produced when $$0.20\,g$$ of this substance is subjected to complete combustion?
A.
$$0.69\,g\,\,{\text{and}}\,\,0.048\,g$$
B.
$$0.506\,g\,\,{\text{and}}\,\,0.086\,g$$
C.
$$0.345\,g\,\,\,{\text{and}}\,\,0.024\,g$$
D.
$$0.91\,g\,\,\,{\text{and}}\,\,\,\,0.72\,g$$
Answer :
$$0.506\,g\,\,{\text{and}}\,\,0.086\,g$$
Solution :
$$\eqalign{
& \% \,C = \frac{{12}}{{44}} \times \frac{{{\text{ mass of }}C{O_2}\,{\text{formed }}}}{{{\text{mass of substance taken }}}} \times 100 \cr
& 69 = \frac{{12}}{{44}} \times \frac{{{\text{ Mass of }}C{O_2}\,{\text{formed }}}}{{0.2}} \times 100 \cr
& \therefore \,{\text{ Mass of }}C{O_2}\,{\text{formed }} = \frac{{69 \times 44 \times 0.2}}{{12 \times 100}} = 0.506\,g \cr
& \% \,H = \frac{2}{{18}} \times \frac{{{\text{ mass of }}{H_2}O\,{\text{formed }}}}{{{\text{ mass of substance taken }}}} \times 100 \cr
& 4.8 = \frac{2}{{18}} \times \frac{x}{{0.2}} \times 100 \cr
& x = \frac{{4.8 \times 18 \times 0.1}}{{100}} \cr
& \,\,\,\,\, = 0.086\,g \cr} $$