Question

The following reaction occurs when a butane cigarette lighter is operated: $C_4{\mathrm{H}}_{10}+{\mathrm{O}}_2⟶{\mathrm{CO}}_2+{\mathrm{H}}_2\mathrm{O}.$ When balancing the equation, you should not start with which element?

Short answer

Do not start with oxygen when balancing this equation.

Step-by-step solution

Identify the Unbalanced Equation

The given chemical reaction is: $C_4{H}_{10}+O_2\to C{O}_2+H_{2}O$. At this stage, the equation is unbalanced, with different numbers of atoms for each element on each side of the equation.

List Elements Involved

The elements involved in the reaction are Carbon ($C$), Hydrogen ($H$), and Oxygen ($O$). Our goal is to have the same number of each type of atom on both sides of the equation.

Choose an Element to Balance Last

When balancing chemical equations, it's strategic to leave oxygen and hydrogen to be balanced last because they often appear in more than one compound. In this equation, oxygen appears in both $O_2$ on the reactant side and in both $C{O}_2$ and $H_{2}O$ on the product side.

Balance Carbon First

Start by balancing the carbon atoms. The reactant $C_4{H}_{10}$ contains 4 carbon atoms, so the products must have 4 carbon atoms as well. Place a coefficient of 4 in front of $C{O}_2$, giving us $C_4{H}_{10}+O_2\to 4C{O}_2+H_{2}O$.

Balance Hydrogen Next

Next, balance the hydrogen atoms. The reactant $C_4{H}_{10}$ contains 10 hydrogen atoms, which means the products must also have 10 hydrogen atoms. Place a coefficient of 5 in front of $H_{2}O$, resulting in $C_4{H}_{10}+O_2\to 4C{O}_2+5H_{2}O$.

Balance Oxygen Last

Finally, balance the oxygen atoms. The products now contain $4\times 2=8$ oxygen atoms from $C{O}_2$ and $5\times 1=5$ oxygen atoms from $H_{2}O$, totaling 13 oxygen atoms. The reactants have $O_2$, which means the coefficient must be adjusted to provide 13 oxygen atoms. Thus, $6.5O_2$ is needed, but since coefficients must be whole numbers, multiply every coefficient in the equation by 2: $2C_4{H}_{10}+13O_2\to 8C{O}_2+10H_{2}O$.

Key concepts

Chemical Reactions

In simple terms, a chemical reaction is a process where substances, called reactants, are transformed into different substances, known as products. This transformation involves the breaking of original chemical bonds and the formation of new ones. It's important to understand that during a chemical reaction, the mass of the products is always equal to the mass of the reactants. This principle is known as the conservation of mass.

Chemical reactions can be represented by chemical equations. These equations show the starting substances and the substances produced. In our exercise, the equation starts with butane ( C_4H_{10} ) and oxygen ( O_2 ) as reactants, which transform into carbon dioxide ( CO_2 ) and water ( H_2O ) as products.

Balancing chemical equations is essential to depict the reaction accurately. It ensures that the number of atoms of each element is the same on both sides of the equation. Think of it like ensuring both sides of a seesaw are level. A balanced equation respects the law of conservation of mass and shows the exact stoichiometric proportions between reactants and products.

Stoichiometry

Stoichiometry is like a recipe for a cookie - it tells you the precise amount of each ingredient you need to get your desired number of cookies. In chemical terms, it refers to the calculation of reactants and products in chemical reactions. It allows chemists to predict how much product they can get from specific amounts of reactants.

In the exercise, stoichiometry involves determining the proportions between butane, oxygen, carbon dioxide, and water based on their chemical formulae. It's important to properly balance chemical equations first, as stoichiometric calculations rely on the coefficients of the balanced equation.

For the given reaction from the exercise, stoichiometry helps us understand that exactly 2 moles of C_4H_{10} react with 13 moles of O_2 to produce 8 moles of CO_2 and 10 moles of H_2O . This ratio is crucial for accurately calculating the amount of each substance involved and produced in the reaction.

Combustion Reaction

Combustion is a type of chemical reaction marked by the reaction of a substance with oxygen, generating heat and light. This process typically involves hydrocarbons, which are compounds made exclusively of hydrogen and carbon, reacting with oxygen to produce carbon dioxide and water.

The combustion reaction in our exercise occurs when butane ( C_4H_{10} ) from a lighter reacts with oxygen. Like most combustion reactions, it releases a significant amount of energy. That's why lighting a lighter releases a flame: a visible sign of energy.

Understanding combustion reactions is vital not just for chemistry, but for everyday applications like internal combustion engines in vehicles or the generation of electricity. They rely on combusting fuels to produce energy, highlighting the importance of balancing such reactions for efficiency and safety.