Acids & Bases

Acids Definition: substances that release hydrogen ions (H+) when mixed in water General formula: HA H is hydrogen A is an anion (non-metal or polyatomic ion) For example: HCl(aq), H2SO4(aq)

Physical Properties of Acids Sour tasting (e.g. lemon juice) Wet to the touch when in solution Water soluble Good conductors of electricity, therefore electrolytes

Chemical Properties of Acids React with metals to produce hydrogen gas Corrosive Make chemical indicators change colour React with bases to produce neutral solution

Bases Definition: substances that release hydroxide ions (OH-) when mixed in water, also called alkaline General Formula: BOH OH is the “hydroxide ion” B is a metal (cation) For example: NaOH(aq)

Physical Properties of Bases Bitter tasting (e.g. tonic water) Slippery to the touch when in solution Water soluble Good conductors of electricity, therefore electrolytes

Chemical Properties of Bases Do not react with metals to produce a gas Corrosive Make chemical indicators change colour React with acids to produce a neutral solution

Chemical Indicators Are solutions that turn different colours in acids and bases Can be either natural or synthetic

Chemical Indicators Indicator ACID NEUTRAL BASE Litmus paper Phenolphthalein Bromthymol blue

pH Scale A numeric scale used to show how acidic or basic a solution is pH stands for “power of hydrogen”

The pH Scale Each step on the pH scale is 10 times difference E.g. a solution with a pH of 3 is 10 times more acidic than a solutions with a pH of 4 E.g. a solution with a pH of 13 is 10 times more basic than a solution with a pH of 12 Practice: How much more acidic is lemon juice (pH 2) than water (pH 7)?

Neutralization Reactions A type of double displacement reaction e.g. HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l) A salt is an ionic compound produced by the reaction of an acid plus a base