Determine the formula of the limiting monohydric alcohol if, upon dehydration of a sample with a volume of 37 ml

| January 8, 2021 | education

Determine the formula of the limiting monohydric alcohol if, upon dehydration of a sample with a volume of 37 ml and a density of 1.4 g / ml, an alkene with a mass of 39.2 g was obtained.

Let’s find the mass of alcohol by the formula.
m = Vp
m = 37 ml × 1.4 g / ml = 51.8 g.
Alcohol formula.
Cn H2n + 2O.
Сn Н2n + 2О = CnH2n + H2O.
The amount of alcohol substance is determined by the formula:
n = m: M.
The molar mass is denoted by x.
n = 51.8 g: x.
The amount of alkene substance will take the expression:
39.2 / x – 18, where 18 is the molar mass of water that is split off from the alcohol molecule.
According to the equation, the amount of alcohol and alkene is the same.
Let’s make a proportion.
51.8 / x = 39.2 / (x – 18).
39.2 x = 51.8 x – 932.4.
932.4 = 51.8 x – 3.2 x,
932.4 = 12.6 x.
x = 932.4: 3.6,
x = 74.
The molar mass of alcohol is 74. Pentanol is C5H11OH.
С5Н11ОН –Н2О → С5Н10 (pentene).



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