Acids and Bases

• Acids and bases dissolve in water; in fact, most liquids are either an acid or a base.
• An acid is a substance that produces hydrogen ions and an anion salt, for example, Hydrochloric acid (HCl) → H+ + Cl-.
• A base is a substance that produces hydroxide ions and a cation salt, for example, Sodium hydroxide (NaOH) → Na+ + OH-.
• A solution with equal amounts of H+ and OH- ions is considered neutral, for example, Water (H2O) → H+A + BOH- → AB + H2O.
• Both acids and bases release ions when dissolved in water, hence they are aqueous.
• The ionic bonds are not strong enough to hold the ions together in water.
• Formulas of acids typically contain Hydrogen, for example, HNO4, HCl, H2SO4.
• Most bases contain hydroxide, for example, NaOH, Ca(OH)2, LiOH.
• Substances containing the compound ammonium are also bases, for example, Ammonium Nitrate (NH4NO3).
• Two very common indicators used by chemists are Litmus Paper and Universal Indicator.
• Litmus Paper changes colour in acidic and basic solutions, for example, Red Litmus Paper in acidic solution, Blue Litmus Paper in basic solution.
• Universal Indicator is a chemical which is made of several compounds that change colour based on pH.
• Many house and garden materials can be used as acid/base indicators, for example, Red cabbage is often used to create indicators.
• Almost any flower, fruit, or plant part that is red, blue, or purple contains pigments called anthocyanins, these compounds change colour when in acidic or alkaline (basic) solutions.
• The pH scale measures the hydrogen ions in a solution, pH stands for “potential of hydrogen”.
• The pH scale is a tool used to measure the acidity or alkalinity of a solution.
• Acids have a pH between 0-6.9, Bases have a pH between 7.1-14.
• The pH scale is exponential, a one unit change on the pH scale corresponds to a ten-fold increase in the concentration of H+ ions, meaning each pH value that is less than 7 is ten times more acidic than the previous one.
• Compare the acidity of solutions with a pH of 6, pH of 3.