7.4 Acids and bases in solution Key concepts: what kinds of ions do acids and bases form in water? What does pH tell you about a solution? What happens in a neutralization reaction? Key terms: hydrogen ion (H+), hydroxide ion (OH-), pH scale, neutralization, salt

Acids and bases in solution An acid is any substance that produces hydrogen ions (H+) in water Acids – the acids we will learn about produce one or more hydrogen ions (H+) and a negative ion in solution with water. The negative ion may be a nonmetal or a polyatomic ion. A hydrogen ion (H+) is an aatom of hydrogen that has lost its electron (oooh noooo!). Hydrogen ions are essential to how acids react.

Acids in solution continued Acids in water solution separate into hydrogen ions (H+) and negative ions. For example: HCl  H+ + Cl- (in water)

Bases in solution A base is any substance that produces hydroxide (OH-) ions in water. Many bases are made of positive ions combined with hydroxide ions. Hydroxide ions (OH-) is a negative ion, made of oxygen and hydrogen. When bases dissolve, the ions separate.

For example: NaOH  Na+ + OH- Not every base has hydroxide ions to begin with, but will still produce hydroxide when reacting with water. Example: NH3 + H2O  NH4+ + OH-

Strengths of acids and bases May be strong or weak. Strength refers to how well an acid or base produces ions in water. Weak acid  very few ions Strong acids  more ions Strong acid examples: hydrochloric (HCl), sulfuric, nitric

Measuring pH pH scale is a range of values from 0 to 14. It expresses the range of hydrogen ions in a solution. A low pH tells you the concentration of hydrogen ions is high, meaning a stronger acid. A high pH tells you the concentration is low. Remember: 7 is neutral. Below that is an acid. Above that is a base.

Acid-base reactions Neutralization – the reaction between an acid and a base Reactants – after neutralization, an acid-base mixture is not as acidic or basic as the starting solutions were. The final pH depends on factors like the volumes, concentrations, and kind of reactants.

Products Salt – any ionic compound that can be made from the neutralization of an acid with a base. A salt is made from the positive ion of a bse and the negative ion of an acid. In a neutralization reaction, an acid reacts with a base to produce a salt and water.