Question

Write a balanced equation for each of the following reactions: (a) \(\mathrm{CH}_{2}=\mathrm{CH}_{2}+\mathrm{O}_{2} \longrightarrow\) (b) \(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}_{2}+\mathrm{H}_{2} \longrightarrow\) (c) \(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}_{3}+\mathrm{Br}_{2} \longrightarrow\)

Short answer

(a) \(\mathrm{CH}_{2}=\mathrm{CH}_{2}+3\mathrm{O}_{2}\rightarrow 2\mathrm{CO}_{2}+2\mathrm{H}_{2}\mathrm{O}\) (b) \(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}_{2}+\mathrm{H}_{2}\rightarrow \mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\) (c) \(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}_{3}+\mathrm{Br}_{2}\rightarrow \mathrm{CH}_{3}-\mathrm{CHBr}-\mathrm{CHBr}-\mathrm{CH}_{3}\)

Step-by-step solution

Identify Reactants and Products for (a)

The reaction is between ethene (\(\mathrm{CH}_{2}=\mathrm{CH}_{2}\)) and oxygen (\(\mathrm{O}_{2}\)). The typical products of a hydrocarbon combustion reaction are carbon dioxide (\(\mathrm{CO}_{2}\)) and water (\(\mathrm{H}_{2}\mathrm{O}\)).

Balance the Equation for (a)

Start by balancing the carbon (C) atoms by placing a coefficient of 2 in front of \(\mathrm{CO}_{2}\). Next, balance the hydrogen (H) atoms by placing a 2 in front of \(\mathrm{H}_{2}\mathrm{O}\). Finally, balance the oxygen (O) atoms by placing a coefficient of 3 in front of \(\mathrm{O}_{2}\). The balanced equation is: \[ \mathrm{CH}_{2}=\mathrm{CH}_{2} + 3\mathrm{O}_{2} \longrightarrow 2\mathrm{CO}_{2} + 2\mathrm{H}_{2}\mathrm{O} \]

Identify Reactants and Products for (b)

In this reaction, propene (\(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}_{2}\)) reacts with hydrogen (\(\mathrm{H}_{2}\)) to form propane (\(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\)). This is a hydrogenation reaction.

Balance the Equation for (b)

Since each component of the reactants and products accounts for the same number of each type of atom on both sides, the equation is already balanced: \[ \mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}_{2} + \mathrm{H}_{2} \longrightarrow \mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{3} \]

Identify Reactants and Products for (c)

The reaction involves butene (\(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}_{3}\)) and bromine (\(\mathrm{Br}_{2}\)) resulting in the formation of dibromo butane (\(\mathrm{CH}_{3}-\mathrm{CHBr}-\mathrm{CHBr}-\mathrm{CH}_{3}\)). This is an electrophilic addition reaction.

Balance the Equation for (c)

Again, each type of atom is already balanced in this addition reaction, so no coefficients are needed. The balanced equation is: \[ \mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}_{3} + \mathrm{Br}_{2} \longrightarrow \mathrm{CH}_{3}-\mathrm{CHBr}-\mathrm{CHBr}-\mathrm{CH}_{3} \]

Key concepts

Balancing Chemical Equations

Balancing chemical equations is an essential skill in chemistry, ensuring that the same number of atoms for each element is present on both the reactant and product sides of the equation. This process respects the Law of Conservation of Mass, which states that matter cannot be created or destroyed, only transformed. To balance an equation, follow these steps:

• Write the unbalanced equation, listing reactants and products.
• Tally the number of atoms for each element in both reactants and products.
• Adjust coefficients (the numbers in front of compounds) to balance each element's atoms on both sides, working one element at a time.
• Re-check your work to ensure that all elements are balanced.

For instance, when balancing a hydrocarbon combustion reaction like with ethene's combustion, start by balancing carbon atoms, then hydrogen, and finally oxygen, giving attention to polyatomic and diatomic molecules.

Hydrocarbon Combustion

Hydrocarbon combustion is a chemical reaction where hydrocarbons (like ethene or propane) react with oxygen to form carbon dioxide and water. This process is highly exothermic, meaning it releases a substantial amount of energy, which can be harnessed for various applications such as powering engines or generating electricity. In a complete combustion, hydrocarbons burn with sufficient oxygen, producing clean products like \\(\text{CO}_2\) and \(\text{H}_2\text{O}\). The general formula for complete hydrocarbon combustion is:\[ \text{C}_x\text{H}_y + \text{O}_2 \longrightarrow \text{CO}_2 + \text{H}_2\text{O} \]To host an efficient combustion process:

• Ensure a proper oxygen supply.
• Use the stoichiometric ratio to calculate necessary reactant quantities.
• Maintain adequate temperature to sustain the reaction.

Hydrocarbon combustion generates carbon dioxide as a byproduct, contributing to greenhouse gas emissions and global warming.

Reaction Types

Chemical reactions can be classified into different types based on how reactants transform into products. Understanding reaction types aids in predicting the behavior of reactions and forming reaction mechanisms. The examples provided here include:

• Combustion reactions: Hydrocarbons mix with oxygen to create carbon dioxide and water.
• Hydrogenation reactions: Hydrogen adds to compounds, often alkenes, transforming them into alkanes, as in propene's conversion to propane.
• Electrophilic addition reactions: Common in organic chemistry where addition of atoms, such as bromine to butene, takes place across carbon-carbon multiple bonds.

Each reaction type has distinct characteristics and underwent different methods for equation balancing. Recognizing these can be crucial for correctly predicting product formation and reaction behavior.

Organic Chemistry

Organic chemistry revolves around the study of carbon-containing compounds and their properties, reactions, and synthesis. It primarily focuses on hydrocarbons such as alkanes, alkenes, and alkynes, as well as their functional derivatives. Key aspects of organic chemistry include:

• The structure and bonding in organic molecules, generally delineated as chains or rings of carbon atoms bonded with other elements, often hydrogen, oxygen, nitrogen, or halogens.
• Understanding isomerism, where compounds with the same molecular formula have different structural arrangements.
• Comprehending reaction mechanisms, which explain the step-by-step electron movement in chemical reactions.
• Exploring the vast diversity of organic reactions, such as substitutions, additions, eliminations, and rearrangements.

In our problem, the focus is primarily on additions and combustion reactions, which are pivotal in transforming hydrocarbons in industrial organic processes.