Acids and alkaline

• Acids in solution are sources of hydrogen ions
• Acids produce H+ ions in aqueous solutions.
• Alkalis produce OH- ions
• A neutral solution has a pH of 7.
• The pH scale measures the acidity or alkalinity
• Match the indicator with its color in alkaline and acidic conditions:

  Phenolphthalein ↔️ Pink in alkaline, colourless in acidic

  Methyl orange ↔️ Yellow in alkaline, red in acidic

  Litmus solution ↔️ Blue in alkaline, red in acidic
• Blue litmus paper turns red in acidic conditions and stays blue
• A higher concentration of H+ ions in a solution means a lower pH.
• As the pH decreases by one unit, the H+ concentration increases by a factor of 10
• Order the steps in the core practical to investigate the change in pH:

  1️⃣ Add dilute HCl to the beaker

  2️⃣ Measure the initial pH

  3️⃣ Add a weighed mass of calcium hydroxide

  4️⃣ Stir and record the pH

  5️⃣ Repeat until no pH change
• Strong and weak acids refer to the concentration of the solution.

  False
• A strong acid fully dissociates
• Weak acids partially dissociate in aqueous solutions.
• A base is any substance that reacts with an acid to form a salt and water
• Alkalis are soluble bases.
• The chemical test for hydrogen uses a burning splint
• Bubbling carbon dioxide through limewater turns it milky.
• Neutralization is a reaction between an acid and a base
• The ionic equation for neutralization is H+(aq) + OH-(aq) → H2O(l).
• Order the steps to prepare a soluble salt from an insoluble reactant:

  1️⃣ Add excess insoluble reactant to the acid

  2️⃣ Ensure the acid reacts completely

  3️⃣ Remove excess reactant by filtration

  4️⃣ The remaining solution is salt and water
• What type of reaction is an acid-alkali neutralization?

  Reaction with water formation
• In an acid-alkali neutralization, hydrogen ions (H+) react with hydroxide ions (OH-) to form water
• The ionic equation for any acid-alkali neutralization is H+(aq) + OH-(aq) → H2O(l)
• Why is excess of an insoluble reactant added when preparing soluble salts from an acid and an insoluble reactant?

  To ensure complete reaction
• Excess insoluble reactant is removed by filtration
• The only products of the reaction between an acid and an insoluble carbonate are salt and water.

  False
• What gas is produced when a carbonate reacts with an acid?

  Carbon dioxide
• When preparing soluble salts from an acid and a soluble reactant, a titration must be used.
• Why is titration necessary when both reactants are soluble?

  To measure exact volumes
• Steps to prepare pure, dry hydrated copper sulfate crystals from copper oxide

  1️⃣ Add excess copper oxide to sulfuric acid

  2️⃣ Filter off unreacted copper oxide

  3️⃣ Evaporate water using a water bath
• When preparing copper sulfate crystals, the acid used is sulfuric
• What color is phenolphthalein in alkaline conditions?

  Pink
• All nitrates are soluble in water.
• Common chlorides are soluble except those of silver and lead
• Which common sulfates are insoluble?

  Lead, barium, calcium
• What is formed when an insoluble salt is produced in a reaction?

  Precipitate
• Steps to prepare a pure, dry sample of an insoluble salt

  1️⃣ Mix the two solutions

  2️⃣ Filter the mixture

  3️⃣ Wash the salt with distilled water

  4️⃣ Dry the salt
• What does the pH scale measure?

  Acidity and alkalinity

  
• The pH scale ranges from 0 to 14.