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Unit 7: Acids & Bases ď Ž

Chapter 8


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


Indicators Indicator

Acid

Base

Neutral

Litmus

Red

Blue

No change

Phenolphthalein

Clear

Pink

Clear

Bromothymol Blue

Yellow

Blue

green


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  

Weak acids and bases ionize or dissociate only slightly in water. HC2H3O2 + H2O H3O+ + C2H3O2- Weak acid NH3 + HOH

Weak base

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.


pH


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) 


pH


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. 

A. LiIO3

B. AgClO3

C. Ba3(PO3)2


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 


The end.

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