Question

Explain why this equation is not balanced and balance it if it can be balanced. \(\mathrm{O}_{2}+2 \mathrm{H}_{2} \mathrm{O}+\mathrm{Br}_{2} \rightarrow 4 \mathrm{OH}^{-}+2 \mathrm{Br}^{-}\)

Short answer

The imbalance was in the oxygen atoms; adding more \(\mathrm{O}_2\) balanced the equation.

Step-by-step solution

Count Atoms on Each Side

First, count the number of atoms of each element present on both sides of the equation. On the left side, we have 2 oxygen atoms (from \(\mathrm{O}_2\)), 4 hydrogen atoms (from \(2 \mathrm{H}_2\mathrm{O}\)), and 2 bromine atoms (from \(\mathrm{Br}_2\)). On the right side, we have 4 oxygen atoms (from \(4 \mathrm{OH}^-\)), 4 hydrogen atoms (from \(4 \mathrm{OH}^-\)), and 2 bromine atoms (from \(2 \mathrm{Br}^-\)).

Compare Atoms

Now, compare the count of each type of atom on the left and right sides: \(\mathrm{O}\) has 2 on the left and 4 on the right, \(\mathrm{H}\) has 4 on both sides, and \(\mathrm{Br}\) has 2 on both sides. The imbalance is only in the oxygen atoms.

Balance Oxygen Atoms

To balance oxygen, adjust the coefficients. The right side has 4 oxygens in \(4 \mathrm{OH}^-\), so we need 4 oxygens in \( \mathrm{O}_2\) on the left. Change \( \mathrm{O}_2 + 2 \mathrm{H}_2\mathrm{O} \) to \( 2 \mathrm{O}_2 + 2 \mathrm{H}_2\mathrm{O} \). This gives 4 oxygen atoms on the left side as well.

Check Hydrogen and Bromine Balance

After adjusting the oxygen, recheck the hydrogen and bromine atoms: 4 hydrogens and 2 bromines are present on both sides. Therefore, all elements are now balanced.

Write the Balanced Equation

Now that all atoms are balanced, the balanced chemical equation is: \[2 \mathrm{O}_{2} + 2 \mathrm{H}_{2} \mathrm{O} + \mathrm{Br}_{2} \rightarrow 4 \mathrm{OH}^- + 2 \mathrm{Br}^-\]

Key concepts

Balanced Chemical Equations

Understanding balanced chemical equations is crucial in chemistry. They ensure that the same number of each type of atom is present on both sides of an equation. This reflects the law of conservation of mass, which states that mass is neither created nor destroyed in a chemical reaction. A balanced equation shows how molecules or compounds react by having equal numbers of each type of atom before and after the reaction.

For example, in the initial equation \( \mathrm{O}_2 + 2 \mathrm{H}_2\mathrm{O} + \mathrm{Br}_2 \rightarrow 4 \mathrm{OH}^- + 2 \mathrm{Br}^- \), each side should have the same total count of atoms for each element. This balancing ensures that the reaction depicted in the equation could actually occur in nature.

Here are the steps for achieving a balanced chemical equation:

• Count the atoms for each element on both sides of the equation.
• Compare these counts to see where the imbalance lies.
• Adjust coefficients (the numbers in front of molecules or atoms) to balance the atoms, starting with the most complex substances first.
• Finally, recheck to ensure that all atoms remain balanced.

By following these steps, you can balance any chemical equation accurately.

Oxygen Atoms Balancing

Balancing oxygen atoms is often a key step in achieving a balanced chemical equation, especially in reactions involving atmospheric oxygen or water. In our example, initially, we have 2 oxygen atoms on the left from \( \mathrm{O}_2 \) but 4 oxygen atoms on the right from \( 4 \mathrm{OH}^- \). This discrepancy calls for balancing.

To solve this, adjust the coefficient of \( \mathrm{O}_2 \) to match the right side, increasing the oxygen to 4 by changing \( \mathrm{O}_2 \) to \( 2 \mathrm{O}_2 \). This balances the oxygen atoms with 4 on each side of the equation.

Proper balancing might involve recalculating coefficients of other species as well, but in this case, it only required the alteration of the \( \mathrm{O}_2 \) coefficient.

Balancing oxygen is crucial because its imbalance often affects the accuracy of the entire equation. Ensuring that the same number of oxygen atoms appear on both sides conserves mass and maintains the context of the reaction.

Hydrogen Atoms Balancing

Balancing hydrogen atoms tends to be straightforward, especially when water is involved, as in the given reaction. Before trying to balance, summarize your hydrogen atoms on each side.

On the left, hydrogen comes primarily from \( 2 \mathrm{H}_2\mathrm{O} \) which yields 4 hydrogen atoms in total (2 molecules of water, each having 2 hydrogen atoms). On the right, \( 4 \mathrm{OH}^- \) correctly reflects the presence of 4 hydrogen atoms.

Replacement or adjustment of coefficients wasn't necessary since both sides already had equal numbers of hydrogen atoms. However, even though our focus was on balancing oxygen, it's always prudent to verify hydrogen balance as it sometimes shifts while balancing other elements.

Reviewing hydrogen ensures that the equation remains fully balanced and accurately represents the chemical reaction. Consistency across all atom types is key to depicting a valid chemical process.

Bromine Atoms Balancing

In chemical equations, ensuring elements like bromine are balanced is equally vital as with any other element. Bromine balancing can sometimes be overshadowed by more predominant elements such as oxygen or hydrogen, yet it's an essential part of an accurate equation.

For bromine, the balancing initially appears correct in the given equation. On the left side, bromine atoms produced from \( \mathrm{Br}_2 \) account for 2 bromine atoms, and on the right, \( 2 \mathrm{Br}^- \) also reflects 2 atoms. Thus, no further adjustment is needed for bromine.

Always elucidate bromine balance concurrently when addressing more abundant elements. Double-check both the left and the right sides once other adjustments are made. Careful tracking avoids unintended imbalance when changes alter compound structures affecting bromine.

Ensuring bromine atoms are rightly balanced confirms the reaction description aligns with actual substance behavior in chemical dynamics.