Acids and Bases Neutralization

Unit 6 - Acids and Bases

​Learning Target

​I know...

• ​the properties of acids and bases.

​Success Criteria

​I can...

• ​explain the difference between acids and bases in terms of pH and color changes in the presence of an indicator.

​pH scale

​pH (potential of Hydrogen)

• a measure of the concentration of H⁺ ions in a solution

  • measured with a pH meter or an indicator with a wide color range (0-14)

​

​Indicators

• ​Indicators are organic substances that change color in an acid or base.

• Examples:

  • litmus - red to blue (or blue to red)

  • phenolphthalein - colorless to pink

  • goldenrod - yellow to red

  • red cabbage juice - pink to green

  ​

​Neutralization

​Question:

​How can we neutralize an extremely acidic solution?

​Neutralization

​Answer:

​Create a chemical reaction between an acid and a base. (This will produce a salt and water.)

​

​Note: Not all neutralization processes will result in a pH of 7. The point of neutralization is to make the effects of the acids or bases less effective. Which will keep it from possibly causing harm.

​Acids

• ​Acids contain at least one hydrogen atom that can be removed when dissolved in water. (proton donors)

  • These form hydronium ions, H₃O⁺. (sometimes shown as only H⁺)

​Bases

• ​Bases form hydroxide ions when dissolved in a water solution.

  • ​These hydroxide ions are written as OH^-

  • bases are proton acceptors

​Acidic Properties

• ​a sour taste

• a pH less than 7

• corrosive

• electrolytes

• to turn litmus paper red

• react with metals to form hydrogen (H₂) gas

​Basic Properties

• bitter taste

• pH greater than 7

• corrosive

• electrolytes

• turn litmus blue

• slippery feel

Strength of Acids and Bases​

​

​How do we know how strong an acid/base is?

• ​Ions can carry an electric charge

  • The strength of an acid or base depends on how completely a compound separates into ions when dissolved in water.

    • ​that is its dissociation

      • definition: ​separation of ions when an ionic compound dissolves in water

    • ​So a strong acid will carry more electricity than weak acid.

​Strong vs Weak

• ​Strong Acid/Base

  • 100% ions in water

  • strong electrolyte

  • will have a very low pH (= acid) or a very high pH (= base)

• ​Weak Acid/Base

  • fewer ions in water = not fully dissociated (broken down) in water

  • weak electrolyte

Electrolytes

Electrolytes get their name from the fact that they conduct electricity in water.

• Example: salt dissolved in water

• Many sports drinks contain “electrolytes” which are salts dissolved in water

​

​Examples

​Weak electrolytes include:

​ammonia, lemon juice (citric acid), and acetic acid

​

​Nonelectrolytes include:

​sugar, oil, and alcohol

​

​Strong electrolytes include:

​sodium hydroxide, sodium chloride (table salt), and hydrochloric acid