A normal alkene contains a double bond at the first carbon atom. 0.7 g of this alkene was added to 1.6 g of bromine

| April 12, 2021 | education

A normal alkene contains a double bond at the first carbon atom. 0.7 g of this alkene was added to 1.6 g of bromine. Determine the alkene formula and name it.

Let’s denote the formula of the unknown alkene as CnH2n.

Let’s write the reaction equation:

CnH2n + Br2 = CnH2nBr2

Let’s find the amount of bromine substance:

v (Br2) = m (Br2) / M (Br2) = 1.6 / 160 = 0.01 (mol).

According to the reaction equation, 1 mol of Br2 reacts with 1 mol of CnH2n, therefore:

v (CnH2n) = v (Br2) = 0.01 (mol).

Let’s find the molar mass of the unknown alkene:

M (CnH2n) = m (CnH2n) / v (CnH2n) = 0.7 / 0.01 = 70 (g / mol).

Let’s compose and solve the equation:

12 * n + 1 * 2n = 70,

n = 5, whence the gross formula of the alkene: C5H10,

a, since the condition says that the alkene is of normal structure (unbranched) and has a double bond at the 1st carbon atom, this is pentene-1 (CH2 = CH-CH2-CH2-CH3).



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