Acid and Base Chemistry

The Use of Hydrochloric Acid (HCl) Is excreted by the stomach lining and acts to: weaken the bonds holding the food together dissolve minerals from various foods kill bacteria which enter our stomach with the food we eat.

pH Is a measure of how acidic a substance is Acid examples  Hydrochloric acid, Sulfuric Acid, Citric Acid It is measured on a scale (pH scale) from 1-14 7 (Neutral) = Water and Blood < 7 (Acidic) = e.g. Vinegar > 7 (Basic) = e.g. Ammonia (household cleaner)

Acids Release hydrogen/hydronium ions in water (H+/H3O+) pH < 7 Ex. HCl(aq)  H+(aq) + Cl-(aq) Balanced because 1 H on the left and right & 1 Cl on the left and right pH < 7 Sour-Tasting Reactive (explosive, corrosive  Handle with Care)

Acids Act as preservatives keeping food good longer Kills microorganisms that make food go bad HCl(aq) + Zn(s)  H2(g) + ZnCl(aq) React with metals to produce Hydrogen Hydrogen is highly combustible!!

Acids Conduct Electricity Although they are molecular compounds, when placed in water they collide with water, breaking the acid into ions. These ions are used to conduct electricity HCl  H+ + Cl- You will notice that the chemical formula for acids start with an H and are followed by an aq. ** The H+ is responsible for the acids properties** Examples: Vinegar, Citric Acid, Lactic Acid

Common Acids Binary Acids – Composed of two elements Acid Name Chemical Formula Use Hydrofluoric Acid HF(aq) Etching glass Hydrochloric Acid HCl(aq) Cleaning concrete Common Oxyacids – Related to Polyatomics Acid Chemical Formula Acetic Acid HC2H3O2(aq) Nitric Acid HNO3(aq)

Acid Precipitation Fossil fuels are made from dead organisms which have been buried underground for millions of years. When fossil fuels (coal, oil, gas) are burned to make energy, nutrients are released which can form undesirable compounds Nitrogen and Sulfur are released which combine with oxygen to form Nitrogen Oxides (NOx) and Sulfur Dioxide (SO2) These then combine with Water (H2O) in the atmosphere to form acids (Nitric Acid - HNO3 & Sulfuric Acid – H2SO4) These acids then fall to earth as acid precipitation in the form of rain, sleet or snow

Acid Precipitation

Effects of Acid Precipitation Forest soils lose valuable nutrients killing plant life Destroy stone work

Effects of Acid Precipitation Can cause series problems in aquatic ecosystems killing fish, amphibians and other organisms due to a decrease in pH

Bases Release Hydroxide Ions in Water (OH-) NaOH(s)  Na+ + OH- Your bases will contain an OH- (Hydroxide) as a reactant pH > 7 Taste Bitter Reactive (Corrosive)  Dangerous Examples: Drain Cleaner, Soap, Antacids

Bases Most Bases are Ionic Compounds and therefore dissolve in water into ions Ba(OH)2(s)  Ba2+(aq) + 2OH-(aq) Since ions are formed in water, bases will conduct electricity Base Name Chemical Formula Use Sodium Hydroxide NaOH(aq) Making paper Calcium Hydroxide Ca(OH)2(aq) Decreasing acidity in lakes and soil

Acids and Bases Video

pH phET online demo Is a measure of how acidic a substance is 7 (Neutral) = Water and Blood < 7 (Acidic) = e.g. Vinegar > 7 (Basic) = e.g. Ammonia (household cleaner) phET online demo