Acids and Bases

• All solutions are either an acid or base, except pure distilled water, which is neutral.
• Acids and bases always consist of mixtures of molecules with water.
• Water breaks down to release H+ ions or OH- ions.

Acids

• Acids release more H+ ions when certain molecules are added to water.
• An acid is a compound that dissolves in water, forming a solution with more H+ ions.
• Acids have a pH of 0-6.9
• Acids contain more H+ ions.
• Examples of acids include vinegar (acetic acid), lemon juice (citric acid), sulfuric acid and hydrochloric acid.
• Acids react with most metals.
• Acids taste sour.
• Acids feel sticky.
• Acids reacts with bases to form salts
• Acids are corrosive

Bases

• Bases release more OH- ions when certain molecules are added to water.
• A base is a compound that dissolves in water, forming a solution with more OH- ions
• Bases have a pH of 7.1-14.
• Bases contain OH- ions.
• Examples of bases include household cleaners, hair conditioner and antacids.
• Bases react with greases and fats.
• Bases taste bitter.
• Bases feel slippery.
• Bases react with acids to form salts.
• Bases are corrosive.

Neutral Solutions

• Pure water (H₂O) is neutral.
• All ions have combined into water molecules.
• Neutral solutions have a pH of 7.0
• Neutral solutions are unreactive.

The pH Scale

• pH is a measure of the hydrogen ion (H+) concentration in a solution.
• pH indicates how acidic or basic a solution is.
• The pH scale ranges from 0 to 14 and is logarithmic.
• Each number on the pH scale is 10 times greater or less than the next.
• A pH of 2 is 10 times more acidic than a pH of 3, and 100 times more acidic than a pH of 4.
• The scale starts at 0, not 1.
• The range of 6.5 - 8.5 pH is considered a healthy level in the environment.

Measuring pH

• pH can be measured with indicators.
• Litmus paper turns red in acid and blue in base.
• Universal indicator has a colour change to show the exact pH level.
• Cabbage juice can be used as an indicator.
• A pH meter gives a very accurate digital reading.
• Phenolphthalein turns pink in the presence of a base.

Neutralization Reaction

• Neutralization occurs when all excess H+ ions in an acid combine with OH- ions in a base to create water.
• In a neutral solution, hydrogen and hydroxide ions are equal in number.
• When an acid and a base react, the products are always salt and water.
• The type of salt produced depends on the type of acid and base that are reacting.
• Example reaction: HCl (Acid) + NaOH (Base) → NaCl (Salt) + H2O (Water)

Practical applications of neutralization

• Antacids can be taken to raise the pH when stomach acid is too acidic (below pH 3).
• The reaction between Tums and stomach acid produces CO2 gas, causing burping.
• Reaction Example: CaCO3 (Calcium Carbonate) + 2 HCl (Acid) → CaCl2 (Calcium Chloride Salt) + H₂O (Water) + CO2 (Carbon Dioxide).
• Acid rain effects can be neutralized by adding natural limestone to acid lakes, which can produce harmful salts.
• pH-balanced shampoos and conditioners are advertised as being less damaging to the hair because they are neutral.
• In a lab, a strong acid can be neutralized by adding the same amount of a strong base.
• For living things, is it better to use a weaker base to neutralize acid.

pH in the Environment

• As acidity (less than 7) or alkalinity (greater than 7) increases, diversity decreases.
• Most living things thrive in the 6.5 - 8.5 pH range.
• Rain is naturally acidic (pH 5.6) due to carbon dioxide combining with water to form carbonic acid.
• Acid rain has a pH less than 4.5.
• Acid rain is caused by burning fossil fuels, which releases sulfur dioxide and nitrogen dioxide into the atmosphere.
• Scrubbers on industrial smokestacks and energy conservation measures can decrease the harmful effects.
• Reaction: Sulfur dioxide + Water → sulfuric acid
• Acid rain's effects are worse in eastern Canada due to acidic rocks (granites), while Alberta's basic rocks (limestones) help neutralize acidity.
• Acid shock occurs in spring when acid snow melts, overwhelming the water's ability to neutralize it, causing a pH drop.

Vocabulary

• pH scale: A logarithmic scale for measuring the acidity of a substance.
• Acids: Sour substances with a pH <7.
• Bases: Bitter substances with a pH >7.
• Neutral: Substances with a pH of 7 that are unreactive.
• Indicators: Chemicals to determine the level of acidity or alkalinity of a solution.
• Litmus paper: Indicates acid (turns red) or base (turns blue).
• Universal indicator: Used to determine the exact pH of a solution.
• pH meter: A digital device for the most accurate pH reading.
• Phenolphthalein: An indicator that turns pink in a base.
• Acidity: How strong the acid is.
• Alkalinity: How strong the base is.
• Carbonic acid: The reason normal rainwater is slightly acidic.
• Acid rain: Precipitation with a pH of less than 5.6.
• Acid shock: Lower pH that occurs in the spring.
• Neutralization: The process involving an acid and base as reactants, producing salt and water.
• Antacids: Bases that neutralize stomach acid.
• Salt: Produced with water from reactions between acids and bases.