Unit 7: Acids & Bases ď Ž
Objective 1: ď Ž
Define acid and describe some of the general properties of an acid.
Warm Up Question Can you write the names and formulas for three acids? Can you name one property of an acid? Can you write the names and formulas for three bases? Can you name one property of a base?
Acids Arrhenius defined an acid as an electrolyte that forms H+ or the hydronium ion in solution. ď Ž There are strong acids and weak acids. HCl, HNO3 and H2SO4 are strong acids. ď Ž
Acids Strong acids completely ionize or break apart in water as shown by the equations below. HCl + H2O
HNO3 + H2O
H2SO4 + H2O
Properties of Acids a. Sour taste b. reactivity with metals c. ability to produce color changes in indicators.
Objective 2: ď Ž
Define base and describe some of the general properties of a base.
Bases Arrhenius defined a base as an electrolyte that forms the hydroxide ion in solution. ď Ž There are strong bases and weak bases. NaOH, KOH, Ca(OH)2 are some strong bases. ď Ž
Bases Strong bases completely ionize or break apart in water as shown by the equations below: NaOH KOH Ca(OH)2
Properties of Bases a. Bitter taste b. slippery feel c. ability to produce color changes in indicators.
Objective 3 Be able to name several common indicators and how they are used to distinguish between an acid and base.
Indicators ď Ž
An indicator is any substance that changes color in the presence of an acid or base.
Indicators Some indicators are paper. The paper has been soaked in a solution that changes color. We will use:
Litmus paper pH paper
Indicators Many solutions act as indicators ď Ž We will use the indicators in the next slide. ď Ž
Lab Properties of Acids & Bases
We will test four solutions with litmus paper and pH paper. We will use 3 commercial indicators: phenolphthalein, bromothymol blue and indigo carmine
We will see if the juice from red cabbage can be used as an indicator.
Objective 4 Know the names and formulas for common acids and bases as given in class.
Warm Up Question Can you name a weak acid? What color is phenolphthalein with a base? What color is litmus with HCl?
Objective 5 Distinguish between strong acids and weak acids, and between strong bases and weak bases. There is a list has been provided to you on a ½ sheet.
Weak acids and bases ionize or dissociate only slightly in water. HC2H3O2 + H2O H3O+ + C2H3O2- Weak acid NH3 + HOH
NH 4+ + OH-
Objective 6 ď Ž
Understand the pH scale and how to use it to distinguish acidic, basic and neutral solutions.
pH scale pH paper turns different colors on a scale of 0-14. ď Ž We will use pH paper to determine if household substances are acidic, basic or neutral. ď Ž
Objective 7 Define pH, and relate pH to hydronium ion concentration in a solution.
pH ď Ž
The greater the hydronium ion concentration the more acidic, the lower the hydronium concentration, the solution is basic. When they are equal, the solution is neutral.
Lab: Testing Household Substances
We will test: Aspirin solution Ammonia Tang Baking soda solution Tap water Borax solution (detergent)
Lab: Testing Household Substances We will use Litmus and pH paper We will use six different commercial indicators We will use three homemade indicators: grape juice, cabbage juice and blueberry juice.
Warm up Question
Which of the following was acidic? Aspirin solution Ammonia Tang Baking soda solution Tap water Borax solution (detergent)
Objective 8: ď Ž
Identify a neutralization reaction, and describe the reactants and products of neutralization.
Neutralization The reaction between an acid and base is called neutralization. Acid + Base Salt + water.
Neutralization Double replacement HCl + NaOH HNO3 + NH4OH
HC2H3O2 + KOH
Objective 9 *The reverse of neutralization is hydrolysis. Investigate the hydrolysis of salts and determine if they are acidic, basic or neutral salts.
Acid/Base Reactions Hydrolysis is the reverse of neutralization. Salt + water acid + base
Steps for Hydrolysis of Salts First add water to the salt. List the ions and their charges. Use your ion sheet. Write a chemical formula. Balance the equation.
Complete the following: NaCl + HOH-> NaNO2 + HOH ->
NH4Cl + HOH ->
Let’s do these together.
Classify the following salts as acidic, basic or neutral.
Objective 10 ď Ž
Explain how electrolytes can be classified.
Electrolytes Strong acids and bases form strong electrolytes. Weak acids and weak bases form weak electrolytes. De-ionized water is a nonconductor.
Lab Hydrolysis of Salts Salts will be mixed with water. The pH of the solution will be determined with Universal Indicator. The solution will be identified as acidic, basic or neutral.
Objective 11 ď Ž
Determine the effectiveness of a variety of antacids
Objective 12 ď Ž
Know how acid rain is formed and steps to prevent.
Lab Commercial Antacids Four different brands of antacid will be tested The indicator bromophenol blue will be used. Stop adding NaOH on blue-purple, or blue. (for maalox stop on green) Determine the best brand