Question

What is the empirical and molecular formula ? What is the molecular weight ?

Computer Unknown #6 Physical Properties 210 200 BP 131-133 °C White solid Sweet odor C 79.22 % H = 5.70% 190 Sodium Fusion Tests Suurvable cha pordion of the sodium fusion filtrate was treated with ferrous state and heated. It was then acidified with dilute sulfuric acid. No observable and was noticed. Another portion of the sodium fusion filtrate was treated with lead acetate. No observable change was noticed. Another portion was acidified and silver nitrate added. No observable change wa noticed. Solubility Test Кеу (.) (-) (.) (+) water 5% hydrochloric acid 5 % sodium bicarbonate 5 % sodium hydroxide conc sulfuric acid Insoluble soluble slightly soluble soluble hot (c) becomes cloudy Classification Tests Beilstein Test. A yellow and blue flame is observed. Combustion - No sooty flame was observed 2,4-DNP. An orange precipitate is formed Tollen's test - no change is observed Jones Reagent (Chromic Acid Test). Within one second a blue green color appeared Potassium permaganate - The purple color is discharged and is replaced by brown precipitate manganese dioxide Iodoform Test - No precipitate is forme

Answer 1

Since the percent amount of C (79.22 %) and H (5.7%) is given, the total is 84.92 %. It means remaining (100- 84.92) = 15.08% is Oxygen.

Why oxygen?

Sodium halogen test is negative, meaning that foreign elements like halogens, sulphur or nitrogen are absent.

Because the compound is soluble in sodium bicarbonate, indicating it is acidic (-OH group). Then it is oxidized by Jones reagent and also shows DNP test (Carbon-oxygen bond is present )

Now, Empirical formula determination:

Name of Element	% of element or gm of element assuming 100 gm of compound	mass of element (in g/mol )	moles of element	ratio
C	79.22	12	6.6	7.02
H	5.7	1	5.7	6.06
O	15.08	16	0.94	1

Note that for calculating the ratio, the lowest value in moles table i.e. 0.94 has been divided by all the three numbers in moles table.

The ratio in whole number is therefore: C: H: O = 7: 6: 1

The empirical formula = C₇H₆O . The empirical mass = 106

The mass spectra shows a peak at 212 = 106 x 2

Hence, the molecular formula is = C₁₄H₁₂O₂

And 212 is the molecular weight of the compound

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