The Characteristic Properties of Acids & Bases (Cambridge (CIE) IGCSE Chemistry)

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  • What is produced when an acid reacts with a metal?

    When an acid reacts with a metal, it produces a salt and hydrogen gas.

  • What is an alkali?

    An alkali is a water-soluble base.

  • What colour does litmus paper turn in acidic conditions?

    In acidic conditions, litmus paper turns red.

  • True or False?

    Thymolphthalein turns blue in alkaline conditions.

    True.

    Thymolphthalein turns blue in alkaline conditions.

  • Why is litmus not suitable for titrations?

    Litmus is not suitable for titrations because its color change is not sharp and it goes through a purple transition color in neutral solutions.

  • What is an indicator?

    An indicator is a substance that changes colour in acidic or alkaline conditions, used to determine the pH of a solution.

  • Define the term neutralisation.

    A neutralisation reaction is a reaction between an acid and a base to form a salt and water.

  • True or False?

    Effervescence is produced when an acid reacts with a metal oxide or hydroxide.

    False.

    Effervescence is produced when an acid reacts with a metal carbonate, due to the formation of carbon dioxide gas.

  • Name the products formed from the reaction between sodium hydroxide and hydrochloric acid.

    The products formed from the reaction between sodium hydroxide and hydrochloric acid are sodium chloride and water.

  • What is the general equation for the reaction of a metal carbonate with an acid?

    The general equation for the reaction of a metal carbonate with an acid is:

    metal carbonate + acid ⟶ salt + carbon dioxide + water

  • Write the word equation for the reaction between sodium carbonate and sulfuric acid.

    The word equation for the reaction between sodium carbonate and sulfuric acid is:

    sodium carbonate + sulfuric acid ⟶ sodium sulfate + water + carbon dioxide

  • What determines the identity of the salt produced in an acid-base neutralisation reaction?

    The identity of the salt produced depends on the acid used and the positive ions in the base.

  • What substances act as bases in acid-base reactions?

    Metal oxides, metal hydroxides and metal carbonates act as bases in acid-base reactions.

  • Which ions causes a substance to be acidic?

    The ion that causes a substance to be acidic is a hydrogen ion / H+.

  • Which ions causes a substance to be alkaline?

    The ion that causes a substance to be alkaline is a hydroxide ion / OH-.

  • What pH is classed as neutral?

    pH 7 is classed as neutral.

  • What pH range is classed as alkaline?

    The pH range for alkaline is 8-14.

  • What pH range is classed as acidic?

    The pH range for an acid is 0-6.

  • True or False?

    The higher the concentration of hydrogen ions in solution, the lower the pH.

    True.

    The higher the concentration of hydrogen ions, the lower the pH.

  • True or False?

    The higher the concentration of hydroxide ions in solution, the higher the pH.

    True.

    The higher the concentration of hydroxide ions in solution, the higher the pH.

  • What is the net ionic equation for neutralisation?

    The net ionic equation for neutralisation is:

    H+  (aq) + OH– (aq)⟶ H2O (l)

  • What is the pH of distilled water?

    The pH of distilled water is 7.

  • Describe how to use universal indicator to test the pH of a substance.

    To measure the pH of a substance with universal indicator:

    • Add a few drops of universal indicator solution to the substance.

    • Check the colour against a colour chart to determine the pH value.

    (Universal indicator paper can also be used).

  • What is a proton donor?

    A proton donor is an acid that ionises in solution producing protons (H+ ions).

  • What is a proton acceptor?

    A proton acceptor is a base that accepts protons donated by an acid.

  • Define strong acid.

    A strong acid is an acid that completely dissociates (or ionises) in water, producing solutions of a very low pH.

  • Define weak acid.

    A weak acid is an acid that partially dissociates (or ionises) in water, producing pH values closer to the middle of the pH scale, while still being below 7.

  • True or False?

    HCl is an example of a strong acid.

    True.

    HCl is an example of a strong acid.

  • What is the equation for the dissociation of HCl in water?

    The equation for the dissociation of HCl in water is:

    HCl (aq) → H+ (aq) + Cl- (aq)

  • True or False?

    Weak acids form an equilibrium in water.

    True.

    Weak acids form an equilibrium in water between molecules and their ions.

  • What is an example of a weak acid?

    An example of a weak acid is propanoic acid (CH3CH2COOH). Carboxylic acids are good examples of weak acids.

  • Define concentrated solution.

    A concentrated solution is a solution that contains a higher number of solute molecules per dm3 of solution.

  • True or False?

    A concentrated acid solution is always stronger than a dilute acid solution.

    False.

    A concentrated acid solution is not always stronger than a dilute acid solution. It depends on the degree of dissociation.

  • What is an oxide?

    An oxide is a compound made from one or more atoms of oxygen combined with one other element.

  • What is an acidic oxide?

    An acidic oxide is an oxide formed when a non-metal element combines with oxygen, reacting with bases to form a salt and water.

  • What is a basic oxide?

    A basic oxide is an oxide formed when a metal element combines with oxygen, reacting with acids to form a salt and water.

  • True or False?

    CO2 is an example of an acidic oxide.

    True.

    CO2 is an example of an acidic oxide.

  • True or False?

    CuO is an example of a basic oxide.

    True.

    CuO is an example of a basic oxide.

  • What type of solution do acidic oxides produce when dissolved in water?

    Acidic oxides produce an acidic solution with a low pH when dissolved in water.

  • What type of solution do basic oxides produce when dissolved in water?

    Basic oxides produce a basic solution with a high pH when dissolved in water.

  • What is an amphoteric oxide?

    An amphoteric oxide is an oxide that can behave as both acidic and basic, depending on whether the other reactant is an acid or a base.

  • Give two examples of amphoteric oxides.

    Two examples of amphoteric oxides are zinc oxide (ZnO) and aluminium oxide (Al2O3).

  • True or False?

    Amphoteric oxides only react with acids.

    False.

    Amphoteric oxides react with both acids and bases.