4.2.4 The pH scale and neutralization

• The pH scale is a measure of the acidity or basicity of a solution.
• Indicators are used to determine the pH of a solution.
• Steps involved in neutralization reactions

  1️⃣ Acid reacts with alkali

  2️⃣ Salt and water are formed
• The pH value is related to the concentration of hydrogen ions (H+) in the solution.
• The pH scale ranges from 0 to 14.
• What is the concentration of hydrogen ions in a neutral solution?

  Balanced
• Each indicator has a specific pH range where it exhibits a color change.
• Neutral solutions have a pH of 7.
• Neutral solutions have a balanced concentration of H+ ions.
• Match the indicator with its pH range and color change:

  Litmus ↔️ 4.5-8.3, Red to Blue

  Phenolphthalein ↔️ 8.3-10, Colorless to Pink

  Methyl orange ↔️ 3.1-4.4, Red to Yellow
• The reaction between HCl and NaOH produces NaCl and H2O.


  True
• Neutralization reactions bring the pH of a solution closer to 7.

  True
• What is the pH of a neutral solution?

  7
• The pH scale ranges from 0 to 14 and measures the acidity or basicity of a solution.


  True
• Acidic solutions have a pH greater than 7.

  False
• What type of reaction occurs when an acid reacts with a base?

  Neutralization
• Steps in a neutralization reaction:

  1️⃣ Acid reacts with a base

  2️⃣ Salt is formed

  3️⃣ Water is produced

  4️⃣ pH shifts closer to 7
• Neutralization reactions are used in wastewater treatment to neutralize acidic industrial waste.


  True
• Solutions with a pH less than 7 are acidic.


  True
• Neutralization reactions produce salt and water.
• A solution with a pH greater than 7 is basic.


  True
• Basic solutions have a low concentration of hydrogen ions (H+).


  True
• Alkaline solutions have a pH greater than 7 and a low concentration of hydrogen ions.


  True
• What is the pH of an acidic solution?

  Less than 7
• Acidic solutions have a pH less than 7.


  True
• Acidic solutions contain a high concentration of hydrogen ions (H+).


  True
• Indicators change color depending on the pH of a solution.


  True
• What are the products of a neutralization reaction?

  Salt and Water
• What is the general balanced chemical equation for a neutralization reaction?

  Acid + Base → Salt + Water
• What is the general balanced chemical equation for a neutralization reaction?

  Acid + Base → Salt + Water
• In neutralization reactions, acids and bases cancel each other out to produce a neutral salt solution and water.

  True
• What is the relationship between pH value and hydrogen ion concentration?

  Inversely related
• Acidic solutions have a high concentration of hydrogen ions.
• Match the indicator with its color change:

  Litmus ↔️ Red to Blue

  Phenolphthalein ↔️ Colorless to Pink

  Methyl orange ↔️ Red to Yellow
• The reaction between hydrochloric acid and sodium hydroxide produces sodium chloride and water.

  True
• In agriculture, lime is used to reduce the acidity of soil.
• The pH scale ranges from 0 to 14.
• Neutralization reactions involve the reaction between acids and alkalis.


  True
• What is the pH of a neutral solution?

  7
• Match the pH range with the solution type:

  0-6 ↔️ Acidic

  7 ↔️ Neutral

  8-14 ↔️ Basic/Alkaline