Acids, Bases, and pH Chapter 9 Section 1

D12 Explain the chemical composition of acids and bases, and explain the change of pH in neutralization reactions.

Learning Target I can differentiate between acids and bases.

Acids When dissolved in water, they ionize (form ions) Form H+ (Hydrogen) ions, which attach to water molecules to form hydronium ions, H3O+ Properties: Taste sour Blue litmus paper turns red Conduct electric current Corrosive

Strong and Weak Acids

Strong Acids HNO3 + H2O H3O+ + NO3- Complete ionization in water High concentration of hydronium ions in the liquid Strong acid Conducts electricity Strong electrolyte Electrolyte: substance that conducts electricity when dissolved in water

Weak Acids CH3COOH + H2O H3O+ + CH3COO- Weak acids Low concentration of hydronium ions in the liquid Do not conduct electricity well Weak electrolyte Double headed arrow Few ions in a solution of acetic acid

Acid Safety Corrosive Can damage living tissues Vapors can be harmful to eyes, mouth and lungs Wear safety goggles, gloves, lab apron

Bases When dissolved in water form OH- (hydroxide ions) Properties Tastes bitter Solution feels slippery Turn red litmus paper blue Like acids, bases can also damage the skin

Strong and Weak Bases

Bases When bases dissolve in water, they ionize. NaOH Na+ + OH- Not all bases contain OH- Some will react with water to form hydroxide ion NH3 + H2O NH4+ + OH-

Strong Bases High concentration of OH- in the solution Ba(OH)2 Ba2+ + 2OH- Complete ionization in water Good conductor of electricity Strong electrolyte

Weak Bases Low concentration of OH- in solution NH3 + H2O NH4+ + OH- Do not ionize completely Not a good conductor of electricity Weak electrolyte

Base Safety Bases are corrosive and can damage living tissue Wear safety goggles, gloves and a lab apron!!

Let’s Review What ions do acids produce? What ions do bases produce? What is the difference between a strong acid and a weak acid? Why should we observe lab safety rules when working with acids and bases?

Learning Target I can explain pH.

Detecting Acids and Bases You can determine if a substance is an acid or a base by using an indicator. An indicator is a substance that changes color in the presence of an acid or base. Indicators measure the level of hydronium ions. The level determines if a substance is acidic or basic.

Indicators Cabbage juice can be used as an indicator Litmus paper is a common indicator Acids turn blue litmus paper red Bases turn red litmus paper blue Only indicates if a substance is an acid or a base To determine strength or weakness, pH values are used catalog.flatworldknowledge.com profmarsolais.com

pH A measure of the concentration of H3O+ ions in solution Acidity or basicity of a solution can be critical Enzymes in your body will not function properly if your blood is too basic or acidic Fish cannot survive in waters that are too acidic or basic ck12.org hapnotes.wikidot.com

Acid: substance that produces H+ ions in aqueous solution Base: substance that produces OH- ions in aqueous solution Neutral Pure H2O Ion Concentration Ion Concentration [OH-] [H+] Stronger Weaker Weaker Stronger 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Bases Acids pH Scale

pH Small differences in pH mean large differences in acidity Example: pH of coke = 3 pH of coffee = 5 Coke is 102 , or 100, times more acidic than coffee. ch302.cm.utexas.edu

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Let’s Review Lemon juice has a pH of 2.2. Is it an acid or a base?

Detergents such as Tide have a pH of about 10 Detergents such as Tide have a pH of about 10. Is Tide an acid or a base?

Seawater has a pH of 8.2. Is seawater an acid or a base?

The inside of your mouth has a pH of 7. Is it an acid or a base?

409 cleaner contains ammonia that has a pH of 12 409 cleaner contains ammonia that has a pH of 12. What will 409 do to red litmus paper?

A soft drink has a pH of 3.2. What will it do to a piece of red litmus paper?

Determining pH You can find pH from the concentration of a strong acid. pH is the negative power of 10 that is used to describe the concentration of H3O+ ions. The concentration of H3O+ in pure water is 1 x 10-7. The pH of pure water = 7

Determining pH The concentration of H3O+ ions in a solution of a strong acid is the same as the concentration of the acid. Determine the pH of a 0.0001 M (Molar) solution of the strong acid HCl. concentration of H3O+ ions = concentration of HCl concentration of H3O+ ions = 0.0001 M = 1 x 10-4 M pH = -(-4) = 4