Question

What is the weight of oxygen that is required for the complete combustion of 2.8 kg of ethylene?
a.) 9.6 kg
b.) 96.0 kg
c.) 6.4 kg
d.) 2.8 kg

Answer 1

Hint: combustion of organic products (complete combustion) always produces carbon dioxide and water. Therefore, in order to solve this question, write the balanced equation for reaction of ethylene and oxygen and use its stoichiometric coefficients to find the weight.

Complete step by step answer:
Let us start this question by writing the molecular formula of ethylene. It is a two-carbon compound and it is an alkene.
Molecular formula of ethylene is \[{{C}_{2}}{{H}_{4}}\].

The reaction for complete combustion of ethylene can be written as –
\[{{C}_{2}}{{H}_{4}}+3{{O}_{2}}\to 2C{{O}_{2}}+2{{H}_{2}}O\]
Molar mass of \[{{C}_{2}}{{H}_{4}}\] (ethylene) = 2 x molar mass of C + 4 x molar mass of H
Molar mass of \[{{C}_{2}}{{H}_{4}}\] (ethylene) = 2 x 12 + 4 x 1 = 28 g
Molar mass of \[{{O}_{2}}\] (oxygen) = 2 x 16 = 32 g
As we can see from the reaction, 3 moles of oxygen are required for the complete combustion of ethylene.
Weight of 3 moles of \[{{O}_{2}}\] (oxygen) = 3 x 32 g = 96 g.

Therefore, we can say that –
28 g of ethylene is combusted by 96 g of oxygen.
1 g of ethylene is combusted by \[\dfrac{96}{28}\] g of oxygen.
2.8 kg of ethylene is combusted by \[\dfrac{96}{28}\text{x}2.8\] kg of oxygen.
Therefore, the weight of oxygen required = \[\dfrac{96}{28}\text{x}2.8\] kg = 9.6 kg.
So, the correct answer is “Option A”.

Note: Ethylene is a colorless flammable gas which has a faint "sweet and musky" odour.
Combustion is also known as burning. It is a high-temperature exothermic redox chemical reaction. As we can see, there is complete oxidation of the organic compound. Therefore, we can say that this is an example of complete combustion.