Acids, Basesand Solutions

Georgia Performance Standard: Students will investigate the properties of solutionsa. Describe solutions in terms of

• Solute/solvent• Conductivity• Concentration

b.Observe factors affecting the rate a solute dissolves in a specific solvent.

c. Determine whether common household substances are acidic, basic or neutral.

Solution -- A homogeneous mixture where one material is dissolved in another… the dissolved particles are so small you can’t see them

Acids and Bases are typically dissolved in water as solutions.

Solubility• The maximum of amount of solute that normally

dissolves in a given amount of solvent at a certain temperature.

• Solubility chart shows how much of a substance will dissolve at a particular temperature.

Soluble--- will dissolve in• Salt is soluble in water.• __________________ is soluble in water.Insoluble– will NOT dissolve in• A _______________ is insoluble in water.• Ink is insoluble in water.

Saturated Solutions Saturated solution– • A solution in which the maximum amount of

solvent has been dissolved. Any more solute added will sit as crystals on the bottom of the container.

Unsaturated solution –•  A solution in which more solute can be

dissolved  Supersaturated solution—• A solution that contains more solute than the

solvent can normally hold at a given temperature 

Solubility chart various materials

Using the graph below answer the following questions…

1.  What is the solubility of KNO3 at 35 degrees Celsius in g/100 cm3 of water?

2. How many grams would dissolve of the KNO3 if you only had 50 cm3 of water?

3.  How many grams would dissolve of the KNO3 if you only had 25 cm3 of water?

4. At what temperature would 30 grams of KClO3 dissolve in 100 cm3 of water?

5.  At what temperature would the solution be saturated if 25 g of KNO3 were present in 100 cm3 of water?

Acids• The simplest acid/base theory defines an

acid as a substance that produces hydrogen ions in solution.

• Acids are made of H+ ions combined with one or more nonmetals

• Examples of common acids– Vinegar, citrus fruits, tomatoes, tea,

carbonated drinks, battery acid

Acids• Acids have distinctive properties

– Have a sour taste

– Turn blue litmus paper red

– Turns red litmus paper red

– Have a pH less than (<) 7

– Can neutralize bases

– React with active metals to produce hydrogen gas

Bases• A base is defined as a substance that

produces hydroxide ions (OH-) in solution

• Bases are metals combined with OH-• Common bases are

–Soap, shampoo, lye, window cleaner, drain cleaner, antacid, ammonia, bleach

Bases• Bases have distinctive properties

–Have a slippery feel–Taste bitter–Turn red litmus paper BLUE–Turn blue litmus paper blue–Have a pH greater than (>) 7–Neutralizes acids

Acids and Bases

• When combined, acids and bases will produce water and a salt.

• The salt forms from the negative ion of the acid and the positive ion from the base.

• The H+ and OH- combine to form water

• This is a NEUTRALIZATION reaction.

Identify the acid, base, salt and water in the neutralization reaction below.

HCl + NaOH NaCl + H2O

Electrolytes

An electrolyte is a compound that produces ions when it dissolves in a solvent (and therefore it is a good conductor of electricity)

Strong Acids are good electrolytes

Weak Acids are poor electrolytes

Strong Bases are good electrolytes

Weak Bases are poor electrolytes

Explain why.

Stronger Acids are better Electrolytes because….

They dissociate more and produce more H+ ions

Stronger Bases BETTER ELECTROLYTESBecause…dissociate more than weaker bases producing More OH- ions…

pH Scale

• The concentration of acids and bases are described by the pH scale

• The pH scale ranges from 0 to 14• The lower the pH the more H+ (acidic)• The higher the pH the more OH- (basic)• Pure water has a pH of 7 and is Neutral• Neutral – having equal numbers of

hydrogen ions and hydroxide ions

pH scale• Some organic compounds change color in

different pH solutions

• These compounds are called indicators because they are used to determine the pH of other materials

Common indicators– Litmus paper (Acid-red/Base-blue)– Phenolphthalein (Acid-no color / Base-pink)– pH paper

– Red Cabbage juice is a natural indicator

pH Scale

• Acidic 0 to 6.00

• Neutral 7

• Basic 7.01 - 14

How to increase rate of solubility of a substance in a solution

1. Crush it

2. heat it

3. Stir it