Question

Write balanced molecular and net ionic equations for the reaction between hydrobromic acid and potassium hydroxide.

Short answer

Balanced molecular equation: HBr + KOH → H2O + KBr. Net ionic equation: H+ + OH- → H2O.

Step-by-step solution

Write the Unbalanced Molecular Equation

Start by writing down the formulas of the reactants and products. Hydrobromic acid is HBr and potassium hydroxide is KOH. Since this is an acid-base reaction, they react to form water (H2O) and potassium bromide (KBr). The unbalanced molecular equation is: HBr + KOH → H2O + KBr.

Balance the Molecular Equation

Count the number of each type of atom on both sides of the equation. There is one H atom in HBr and one H atom in KOH, which combine to make two H atoms in H2O. This means we need to balance our equation with coefficients to ensure that we have the same number of atoms on each side. The balanced molecular equation is: HBr + KOH → H2O + KBr, which is already balanced as written.

Write the Total Ionic Equation

Dissociate all strong electrolytes into their ions. Both HBr and KOH are strong electrolytes and will dissociate completely. The total ionic equation is: H+ + Br- + K+ + OH- → H2O + K+ + Br-.

Identify and Remove the Spectator Ions

Spectator ions are ions that do not participate in the actual reaction. In this case, the potassium (K+) and bromide (Br-) ions are spectator ions. After removing them, we are left with the net ionic equation.

Write the Net Ionic Equation

The net ionic equation includes only the species that are involved in the reaction. Remove the spectator ions to find the net ionic equation, which is: H+ + OH- → H2O.

Key concepts

Acid-Base Reactions

Acid-base reactions are a staple in chemistry, representing a process where an acid and a base react to form water and a salt. This fundamental chemical reaction is also known as a neutralization reaction. When we look at hydrobromic acid (HBr) reacting with potassium hydroxide (KOH), we are observing a classic acid-base reaction. Here, hydrobromic acid donates a proton (H+) to the hydroxide ion (OH-) from the potassium hydroxide, resulting in the formation of water (H₂O) and potassium bromide (KBr), a salt.

Stoichiometry

Stoichiometry is the section of chemistry that pertains to the calculation of reactants and products in chemical reactions. It is heavily based on the conservation of mass and the law of definite proportions. Every balanced chemical equation adheres to the stoichiometry of the reaction, meaning that the number of atoms of each element in the reactants must equal the number of atoms of those elements in the products. This concept is crucial when writing balanced chemical equations, like in the hydrobromic acid and potassium hydroxide example, where the correct stoichiometry ensures we have one potassium atom, one bromine atom, and two hydrogen atoms on each side of the balanced molecular equation.

Balancing Chemical Equations

Balancing chemical equations is an essential skill in chemistry, as it reflects the law of conservation of mass. We must have the same number of each type of atom on both sides of the equation. This concept is beautifully exemplified when we balance the molecular equation for the reaction of hydrobromic acid with potassium hydroxide. Each atom type is counted and coefficients are adjusted to ensure balance. Fortunately, in our example, each side already has one of bromine and potassium atoms, and two of hydrogen, so no further balancing is required. However, the principle remains that attaining balance is critical for accurately representing chemical reactions.