A. A well-known reagent in analytical chemistry, dimethylglyoxime, has the empir

Question

A. A well-known reagent in analytical chemistry, dimethylglyoxime, has the empirical formula C2H4NO. If its molar mass is 116.1 g/mol, what is the molecular formula of the compound?

B. Nitrogen and oxygen form an extensive series of oxides with the general formula NxOy. One of them is a blue solid that comes apart, reversibly, in the gas phase. It contains 36.84% N. What is the empirical formula of this oxide?

C. The characteristic odor of pineapple is due to ethyl butyrate, an organic compound which contains only carbon, hydrogen and oxygen. If a sample of ethyl butyrate is known to contain 0.62069 g of carbon, 0.103448 g of hydrogen and 0.275862 g of oxygen, what is the empirical formula for ethyl butyrate?

Explanation / Answer

Part A

empirical formula is C2H4NO

empirical formula weight = 58

The ratio between molar mass and empirical formula mass = 116.1/58=2.001 =2

Thus the molecular formula = 2x[C2H4NO]

= C4H8N2O2

Part B

element N O

percentage 36.84 63.16

moles of atoms 36.84/14=2.58 63.16/16 = 3.94

The ratio of moles 1 1.53

making it whole 2 3

Thus the empirical formula is N2O3 which is ablue solid at low temperatures.

Part C

element C H O

0.62069 0.103448 0.275862 g

moles 0.051 0.103448 0.017

ratio 3 6 1

Thus the empirical formula is C3H6O

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