The yellow binary compound X1 was completely dissolved in concentrated nitric acid by heating, the g — Organic Chemistry Chemistry Question
From one yellow powder to another: A simple inorganic riddle
The yellow binary compound X1 was completely dissolved in concentrated nitric acid by heating, the gas evolved is 1.586 times denser than air. Upon adding an excess of barium chloride to the solution formed a white solid X2 precipitates. It was filtered. The filtrate reacts with an excess of silver sulfate solution forming a precipitate of two solids X2 and X3, also separated from solution by filtration. To the new filtrate the solution of sodium hydroxide was being added drop-wise until the solution became nearly neutral (about pH 7). At this time a yellow powder X4 (77.31 wt.% of Ag) crystallized from the solution. The mass of X4 is nearly 2.4 times larger than that the mass of the first portion of X2.
Determine the chemical formulae of X1 – X4.
Model Answer
The precipitate X2 formed by addition of barium chloride in acidic medium is barium sulfate BaSO4.
The precipitate X3 formed by addition of silver sulfate is silver chloride AgCl.
The yellow precipitate X4 formed by addition of alkali can be mercury oxide HgO or silver phosphate Ag3PO4. The ratio of molar masses X4 : X2 is 0.931 for HgO : BaSO4 which is not valid and 1.798 for Ag3PO4 : BaSO4 which gives 2.4 being multiplied by 4/3. So, the molar ratio is 4 Ag3PO4 : 3 BaSO4 which corresponds to P : S = 4 : 3, i.e. to formula P4S3 of X1.
X1 = P4S3 X2 = BaSO4 X3 = AgCl X4 = Ag3PO4
Determine the chemical formula of the gas and provide equations for all reactions in ionic or non-ionic form.
Model Answer
The gas evolved has a molar mass 1.586 × 29 = 46 g mol-1.
In the structural unit of X1 all atoms of only one element are in equivalent positions. Draw the structure of X1.
Model Answer
Phosphorus sulfide P4S3 is a molecular cage
Predict the products of X1 interaction with:
a) excess oxygen;
b) excess of hot concentrated sulfuric acid;
c) solid KClO3 with grinding.
Write down the equations of the reactions.
Model Answer
a) P4S3 + 8 O2 = 2 P2O5 + 3 SO2
b) P4S3 + 16 H2SO4 = 4 H3PO4 + 19 SO2 + 10 H2O
(oxidation of sulfide to S instead of SO2 is also acceptable)
c) 3 P4S3+ 16 KClO3 = 16 KCl + 6 P2O5 + 9 SO2