Question

Неизвестный алкен 7 г присоединяет бромоводород, объём которого одинаков с объёмом метана массой 2 г (н.у.) Найдите молекулярную формулу алкена и напишите структурные формулы его изомеров.

Answer 1

N(CH4)=2/16=0,125моль
V(CH4)=0,125×22,4=2,8л
n(HBr)=2,8/22,4=0,125моль=n(CnH2n)
Mr(CnH2n)=7/0,125=56г/моль
Составим и решим уравнение:
14n=56
n=4
C4H8 - бутен

Answer 2

Alkene Molecular Formula and Structural Isomers

To determine the molecular formula and structural isomers of the unknown alkene, we need to analyze the given information.

According to the question, an unknown alkene with a mass of 7 g reacts with an equal volume of bromine water (HBr) to form a product. The volume of HBr is the same as the volume of methane (CH4) with a mass of 2 g at standard conditions (n.u.).

To find the molecular formula of the alkene, we can start by calculating the number of moles of methane using its mass and molar mass. The molar mass of methane (CH4) is 16 g/mol (12 g/mol for carbon and 4 g/mol for hydrogen).

The number of moles of methane can be calculated using the formula:

Number of moles = Mass / Molar mass

For methane: Number of moles = 2 g / 16 g/mol = 0.125 mol

Since the volume of HBr is the same as the volume of methane, we can assume that the number of moles of HBr is also 0.125 mol.

Now, let's consider the reaction between the alkene and HBr. The reaction involves the addition of HBr across the double bond of the alkene, resulting in the formation of a halogenated alkane.

The balanced chemical equation for the reaction can be written as:

Alkene + HBr → Halogenated alkane

Since the volume of HBr is the same as the volume of methane, we can assume that the number of moles of HBr is equal to the number of moles of the alkene.

Therefore, the number of moles of the alkene is also 0.125 mol.

Now, let's calculate the molar mass of the alkene using its mass and the number of moles.

The molar mass of the alkene can be calculated using the formula:

Molar mass = Mass / Number of moles

For the alkene: Molar mass = 7 g / 0.125 mol = 56 g/mol

The molar mass of the alkene is 56 g/mol.

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