1. A hydrocarbon is composed of 84.72% (by mass) of carbon. It has a molar mass of 200. g/mol. What
is its molecular formula?
2. Alka-Seltzer uses the reaction of sodium bicarbonate with citric acid in aqueous solution to produce
a fizz. Balance the following reaction. What mass of
should be used for every 1.0x102 mg of
? What mass of
(g) could be produced by this mixture? (Note sodium citrate
, water, and carbon dioxide are produced.
3. A confiscated white substance, suspected of being cocaine, was purified by a forensic chemist and
subjected to elemental analysis. Combustion of a 50.86-mg sample yielded 150.0 mg
and
46.05 mg
. Analysis for nitrogen showed that the compound contained 9.39% nitrogen by mass.
The formula of cocaine is
. Can the forensic chemist conclude that the suspected
compound is cocaine?