Question 1:

The correct answer is D. 2 and 3 only (metal oxide and metal carbonate).

Reasoning:

Copper(II) sulfate (CuSO₄) is a soluble salt that can be prepared by reacting dilute sulfuric acid with a suitable copper compound.

• Method 1 (Metal): Copper is below hydrogen in the reactivity series. This means it does not react with dilute acids (such as sulfuric acid) to produce a salt and hydrogen gas. So, this method cannot be used to prepare copper(II) sulfate.

• Method 2 (Metal oxide): Copper(II) oxide (CuO) is a basic oxide. It reacts with dilute sulfuric acid to produce copper(II) sulfate and water:
  CuO + H₂SO₄ → CuSO₄ + H₂O
  This method can be used.

• Method 3 (Metal carbonate): Copper(II) carbonate (CuCO₃) reacts with dilute sulfuric acid to produce copper(II) sulfate, water, and carbon dioxide:
  CuCO₃ + H₂SO₄ → CuSO₄ + H₂O + CO₂
  This method can also be used.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 2:

The correct answer is D. the solid stops disappearing.

Reasoning:

In this experiment, you are adding excess zinc oxide (a white powder) to dilute hydrochloric acid. The reaction is:

ZnO + 2HCl → ZnCl₂ + H₂O

• Zinc oxide is a base that neutralizes the acid. As long as there is acid present, the zinc oxide will continue to react and dissolve (disappear) into the solution to form soluble zinc chloride.

• Once all the acid is neutralized, any additional zinc oxide added will no longer react. This means the solid will stop disappearing and will remain as undissolved powder at the bottom of the beaker (since it is in excess).

Why the others are incorrect:

• A. the reaction stops fizzing – Zinc oxide reacting with hydrochloric acid does not produce a gas (no fizzing). This reaction produces only salt and water. Fizzing would indicate a carbonate reacting, not an oxide.

• B. the solution turns green – Zinc compounds are not green; copper compounds are green/blue. This is not a valid indicator for this reaction.

• C. the solid changes colour – Zinc oxide is white and remains white; it does not change colour during the reaction.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 3:

The correct answer is A. zinc chloride + water.

Reasoning:
The reaction described is between zinc oxide (ZnO) and dilute hydrochloric acid (HCl). This is a standard neutralization reaction between a metal oxide (base) and an acid.

• The acid is hydrochloric acid (HCl).

• The base is zinc oxide (ZnO).

When a metal oxide reacts with an acid, the products are always:
Metal oxide + Acid → Salt + Water

Here:

• The salt formed is zinc chloride (ZnCl₂) because zinc (from the oxide) combines with chloride (from the acid).

• The other product is water (H₂O).

The balanced chemical equation is:
ZnO + 2HCl → ZnCl₂ + H₂O

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 4:

The correct answer is B. condenser.

Reasoning:

To prepare zinc sulfate crystals from excess zinc carbonate and dilute sulfuric acid, the steps are:

1. React the zinc carbonate with the acid in a beaker (equipment C).

2. Filter off the excess solid zinc carbonate using a filter funnel and filter paper (equipment D).

3. Evaporate some of the water from the filtrate using an evaporating basin (equipment A) and gentle heating.

4. Cool the concentrated solution to allow crystals to form.

A condenser is used in distillation to cool and condense vapors back into a liquid. Since you are only evaporating the solution to remove water (not collecting or condensing the vapor), a condenser is not required in this preparation.

Why the others ARE required:

• A. Evaporating basin – Required to heat and evaporate water from the solution to concentrate it.

• C. Beaker – Required to hold the acid and zinc carbonate during the reaction.

• D. Filter funnel – Required to filter out the excess unreacted zinc carbonate after the reaction is complete.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 5:

The correct answer is A. the reaction stops fizzing.

Reasoning:

In this experiment, you are adding excess zinc carbonate to dilute sulfuric acid. The reaction is:

ZnCO₃ + H₂SO₄ → ZnSO₄ + H₂O + CO₂

• Zinc carbonate reacts with the acid to produce carbon dioxide gas, which causes fizzing (effervescence).

• As long as there is acid present, adding more zinc carbonate will continue to produce fizzing.

• Once all the acid is neutralized, any further zinc carbonate added will not react, so the fizzing will stop.

Since you are adding the zinc carbonate in excess, the solid will remain at the bottom after neutralization. Therefore, the stopping of fizzing is the clear indicator that the acid has been fully neutralized.

Why the others are incorrect:

• B. the solution turns green – Zinc salts are colourless (or white when solid); a green colour would indicate a copper compound, not zinc. This is not relevant here.

• C. the solid changes colour – Zinc carbonate is white and remains white; it does not change colour during the reaction.

• D. the solid has all disappeared – This is incorrect because you are adding the zinc carbonate in excess, meaning you deliberately add more than enough to neutralize the acid. Therefore, some solid will always remain after neutralization, so it will not all disappear.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 6:

The correct answer is C. to ensure that all the dilute sulfuric acid has reacted.

Reasoning:
In preparing a soluble salt like zinc sulfate by reacting an insoluble base (zinc carbonate) with an acid, the excess solid is used to ensure that all of the acid is fully neutralized.

• If you used exactly the right amount of zinc carbonate, it would be very difficult to know when the reaction is complete, and you might end up with unreacted acid in your solution.

• By adding the solid in excess, you guarantee that there is more than enough zinc carbonate to react with every last particle of sulfuric acid. Once the acid is fully consumed, any remaining zinc carbonate simply sits undissolved at the bottom of the mixture.

• The excess solid is then easily removed by filtration, leaving behind a pure solution of zinc sulfate.

Why the others are incorrect:

• A is wrong because producing carbon dioxide is a result of the reaction, not the reason for using excess zinc carbonate. The goal is to neutralize the acid, not to make gas.

• B is wrong because the speed of the reaction is not the reason for using excess; the reason is about ensuring complete neutralization.

• D is wrong because it is the acid you want to ensure has fully reacted, not the zinc carbonate. The zinc carbonate is deliberately left over (in excess) so you know the acid is gone.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 7:

The correct answer is A. filtration.

Reasoning:
In this preparation, after the reaction between zinc carbonate and dilute sulfuric acid is complete, you have a mixture containing:

• A solution of zinc sulfate (the soluble salt you want).

• Excess, unreacted zinc carbonate (an insoluble solid).

Since the zinc carbonate is an insoluble solid and the zinc sulfate is in solution, the best way to separate them is by filtration. The liquid (zinc sulfate solution) passes through the filter paper as the filtrate, while the excess solid zinc carbonate remains on the filter paper as the residue.

Why the others are incorrect:

• B. Crystallisation – This is used after filtration to obtain solid zinc sulfate crystals from the solution (by evaporating water and cooling). It does not remove excess solid from the mixture.

• C. Distillation – This is used to separate a liquid from a solution by boiling and condensing the vapor (e.g., to collect pure water). It is not used to remove an insoluble solid.

• D. Dissolving – This would not work because the zinc carbonate is already insoluble; it does not dissolve, so it cannot be removed this way.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 8:

The correct answer is B. crystallization.

Reasoning:

After filtering off the excess zinc carbonate, you are left with an aqueous solution of zinc sulfate (the filtrate). To obtain solid zinc sulfate crystals from this solution, you need to remove the water. This is done by:

1. Partial evaporation of the water using an evaporating basin (to concentrate the solution).

2. Cooling the concentrated solution, which causes the zinc sulfate to form solid crystals as its solubility decreases with temperature.

This entire process is called crystallization.

Why the others are incorrect:

• A. Filtration – This is used to separate an insoluble solid from a liquid. At this stage, the zinc sulfate is already dissolved in the solution, so filtration cannot separate it from the water.

• C. Distillation – This is used to collect a liquid (e.g., pure water) by boiling and condensing it. It would remove all the water but leave behind a solid residue (which could be crystals), but distillation is not the standard method for preparing salt crystals—it is used when you want to collect the liquid.

• D. Dissolving – This would do the opposite; it would mix the zinc sulfate back into solution, not obtain solid crystals from it.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 9:

The correct answer is C. neutralization and filtration.

Reasoning:

1. Neutralization: When you add magnesium oxide (a base) to dilute hydrochloric acid, a neutralization reaction occurs, producing magnesium chloride and water:
   MgO + 2HCl → MgCl₂ + H₂O
   This is the chemical process that forms the soluble salt.

2. Filtration: Since you add the magnesium oxide in excess (to ensure all the acid is neutralized), some unreacted magnesium oxide will remain as an insoluble solid in the mixture. This excess solid is then removed by filtration, leaving a pure magnesium chloride solution.

Why the others are incorrect:

• A (precipitation and filtration): Precipitation is the formation of an insoluble solid from two solutions. This does not occur here; magnesium chloride is soluble and remains in solution.

• B (precipitation and distillation): Precipitation does not occur, and distillation is not needed (you are not collecting the water vapor; you want the salt solution).

• D (neutralization and distillation): While neutralization does occur, distillation is not involved. You only need to filter off the excess solid, not distill the solution (distillation would be used if you wanted to collect pure water or separate liquids).

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 10:

The correct answer is D. Heat to partially evaporate the solution / Dry crystals using filter paper or a paper towel.

Reasoning:

To obtain pure, dry hydrated copper(II) sulfate crystals from a solution, you must be careful not to drive off the water of crystallization. Here’s why the correct steps are:

1. Heat to partially evaporate the solution:
   You should only evaporate some of the water to concentrate the solution. Heating to dryness (evaporating all the water) would leave an anhydrous powder, not large, well-formed hydrated crystals (CuSO₄·5H₂O). It could also cause the salt to decompose if overheated.

2. Dry crystals using filter paper or a paper towel:
   After the crystals form upon cooling, you separate them from the remaining solution (e.g., by filtration) and then gently pat them dry with filter paper or a paper towel at room temperature.
   Drying them in a hot oven would drive off the water of crystallization, turning the blue hydrated crystals into a white anhydrous powder.

Why the others are incorrect:

• A: Heating to evaporate all the water destroys the hydrated crystals, and drying in a hot oven removes the water of crystallization.

• B: Heating to evaporate all the water destroys the hydrated crystals (even though the drying method is correct).

• C: While partial evaporation is correct, drying in a hot oven would remove the water of crystallization and ruin the hydrated crystals.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.