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CHEM VALIDATION TEST T2 (COSMIC)

03/06/2025

YEAR 10 AP CHEMISTRY - Cosmic Acid Validation Test - ANSWER SHEET

STUDENT NAME: [kmaba]

TEACHER: [Br Oussama]

DATE: [3/06/25]

Section 1: Data Analysis [21 marks]

The aim of your investigation was “to understand how acids react with other substances and use this information to decide on a better container for Cosmic Acid” .

  1. Based on the results of your experiment, was there any pattern or trend when an acid was tested with a metal hydroxide? (2 marks)

    Based on our experimental results, there was no visually vigorous reaction (like gas production or significant temperature change noted) when acids (Hydrochloric Acid, Sulfuric Acid, Nitric Acid) were tested with Calcium Hydroxide or Barium Hydroxide. The observations were consistently recorded as “Nothing” or “(dissolved) Nothing.” This suggests that, under the conditions of our experiment, metal hydroxides did not show an obvious, rapid chemical reaction with the acids tested beyond dissolution.

  2. Based on the results of your experiment, was there any pattern or trend when an acid was tested with a metal carbonate? (2 marks)

    Yes, a clear pattern was observed. When acids were tested with metal carbonates (Calcium Carbonate and Sodium Hydrogen Carbonate), there was always a reaction involving bubbling or fizzing. For example, Calcium Carbonate “Bubbled, Fizzy” or “Bubbled Alot,” and Sodium Hydrogen Carbonate showed “Intense Bubbling” and sometimes “smoke.” This indicates the production of a gas.

  3. Based on the results of your experiment, was there any pattern or trend when an acid was tested with a solid metal? (2 marks)

    Yes, there was a discernible pattern related to the type of metal. Magnesium metal reacted vigorously with all acids, producing “Smoking and Hydrogen gas.” Zinc metal also reacted with all acids, showing “Bubbles Formed” (though “Less bubbles formed” with Nitric Acid). In contrast, Aluminum metal showed “Nothing” (no observable reaction) with all three acids tested. This suggests varying reactivity of metals with acids.

  4. Based on the results of your experiment, would any of the substances tested be suitable for use as a container for Cosmic Acid? Explain your answer. (2 marks)

    Based on our experimental results, Aluminum Metal would be the most suitable substance tested for a container for Cosmic Acid. This is because aluminum showed “Nothing” (no observable reaction) when tested with Hydrochloric Acid, Sulfuric Acid, and Nitric Acid. Other materials like Zinc, Magnesium, Calcium Carbonate, and Sodium Hydrogen Carbonate all showed reactions. While Calcium Hydroxide and Barium Hydroxide also showed “Nothing” or “(dissolved) Nothing,” metals are generally more structurally sound for containers, and aluminum specifically did not react.

While a group of Year 10 AP students are sitting for their test in the exam hall, some cosmic acid is spilled in the laboratory upstairs. It is eating its way through the floor and threatens the student below. The principle, Br Khan, rushes into the exam hall. Knowing the students had been experimenting with acids, he sought their advice.

a) The students are faced with a ghastly death as cosmic acids drips from the ceiling. Choose one of the substances you tested be used to counteract the acid and save the students? Explain your choice. (2 marks)

I would choose Sodium Hydrogen Carbonate (NaHCO₃). Our experiments showed that Sodium Hydrogen Carbonate reacted with “Intense Bubbling” and “smoke” when mixed with acids. This indicates a rapid and vigorous reaction, which would be effective in neutralizing the dangerous cosmic acid quickly. Calcium Carbonate would also be a good alternative as it also “Bubbled Alot.”

b) Cosmic acid has the chemical formular H3Xe9MoF8. When cosmic acid dissolves in water, it ionises to produce the xenomorph ion Xe9MoF8+3. Write the chemical equation for the reaction that will occur when cosmic acid reacts with the substance that you chose in part a) (2 marks)

Assuming Cosmic Acid (H₃Xe₉MoF₈) acts as a triprotic acid (donating 3 H⁺ ions) and reacts with Sodium Hydrogen Carbonate: H₃Xe₉MoF₈(aq) + 3NaHCO₃(s) → Na₃Xe₉MoF₈(aq) + 3H₂O(l) + 3CO₂(g)

(Note: The formation of a “xenomorph ion Xe9MoF8+3” from an acid with formula H₃Xe₉MoF₈ is chemically unusual. The equation above assumes standard behavior where H₃Xe₉MoF₈ donates 3H⁺ and forms the anion Xe₉MoF₈³⁻).

c) Before Br Khan can return upstairs with your advice, a student pours a beaker of water onto the cosmic acid in an effort to dilute it. The diluted acid immediately starts to boil and such intense heat is given off that wooden furniture burst into flames. Explain why this happened. Include a relevant chemical equation as part of your explanation. (3 marks)

This happened because the process of dissolving and ionizing concentrated Cosmic Acid in water is highly exothermic. When water was added, a large amount of heat energy was released very rapidly. This intense heat caused the solution’s temperature to rise sharply, leading to boiling. The heat generated was sufficient to reach the ignition temperature of the wooden furniture, causing it to burst into flames.

Relevant chemical process (representing dissolution and ionization): H₃Xe₉MoF₈(conc) + H₂O(l) → 3H⁺(aq) + Xe₉MoF₈³⁻(aq) ΔH << 0 (highly exothermic)

d) While the flames burnt around it, the cosmic acid dripped onto the expensive new marble floor of the lab. As the cosmic acid dissolved its way through the marble, it bubbled vigorously, and the flames quickly died out. Using the fact that marble is a form of calcium carbonate, explain why this happened. Include a relevant chemical equation as part of your explanation. (3 marks)

Marble is a form of calcium carbonate (CaCO₃). When the Cosmic Acid reacted with the calcium carbonate, a neutralization reaction occurred which produced carbon dioxide gas (CO₂), water, and a salt. The vigorous bubbling was the CO₂(g) being released. Carbon dioxide is denser than air and does not support combustion. As large quantities of CO₂ were produced, it displaced the oxygen around the fire, effectively smothering the flames and causing them to die out.

Chemical equation: 2H₃Xe₉MoF₈(aq) + 3CaCO₃(s) → Ca₃(Xe₉MoF₈)₂(aq) + 3H₂O(l) + 3CO₂(g)

e) The cosmic acid continued to eat its way through the floor, and it reached the iron girders below. As it reacted with the iron girders, a gas was given off. After a few minutes, there was an explosion with a loud pop. Explain why this happened. Include a relevant chemical equation as part of your explanation. (3 marks)

The iron (Fe) in the girders reacted with the Cosmic Acid. Active metals like iron react with acids to produce hydrogen gas (H₂). Hydrogen gas is highly flammable and forms an explosive mixture with oxygen in the air. The gas given off was hydrogen, which accumulated. The “loud pop” indicates that this hydrogen-air mixture was ignited (possibly by the existing fire, a spark, or the heat of the reaction), causing a small explosion.

Chemical equation (assuming iron forms Fe³⁺ ions with the strong cosmic acid): 2H₃Xe₉MoF₈(aq) + 2Fe(s) → 2FeXe₉MoF₈(aq) + 3H₂(g)

(Alternatively, if Fe forms Fe²⁺: 2H₃Xe₉MoF₈(aq) + 3Fe(s) → Fe₃(Xe₉MoF₈)₂(aq) + 3H₂(g). Both produce H₂(g).)

Section 2: Questions [24 marks]

  1. Acids are covalent molecules that ionise when they are dissolved in water. (3 marks)

    • What species of ions are always produced when an acid ionises?

      Hydrogen ions (H⁺) (which in aqueous solution can also be represented as hydronium ions, H₃O⁺).

    • What range of pH does an acid have?

      pH less than 7 (pH < 7).

    • Metal hydroxides are an example of a base. A metal hydroxide dissociates when it is dissolved in water. What is the species of ion produced when a metal hydroxide is dissolved in water that identifies it as a base?

      Hydroxide ions (OH⁻).

  2. Complete the following table by writing either the name or the chemical formular for each acid. (2 marks)

    NameChemical formula
    Carbonic AcidH₂CO₃
    Phosphoric AcidH₃PO₄

  3. Complete the following table by writing either the name or the chemical formular for each base. (2 marks)

    NameChemical formula
    AmmoniaNH₃
    Sodium carbonateNa₂CO₃

  4. Write the balanced chemical reaction, including state variables, for each of the following reactions: (Remember, for an acid to be dilute, it must be in aqueous solution) (8 marks)

    • Dilute sulfuric acid and solid potassium hydroxide: H₂SO₄(aq) + 2KOH(s) → K₂SO₄(aq) + 2H₂O(l)

    • Dilute phosphoric acid and sodium carbonate solution: 2H₃PO₄(aq) + 3Na₂CO₃(aq) → 2Na₃PO₄(aq) + 3H₂O(l) + 3CO₂(g)

    • Dilute carbonic acid and ammonia solution: H₂CO₃(aq) + 2NH₃(aq) → (NH₄)₂CO₃(aq)

    • Sulfur dioxide and aqueous sodium hydroxide: SO₂(g) + 2NaOH(aq) → Na₂SO₃(aq) + H₂O(l)

  5. Not all metals react with acids. The Metal Activity Table should be used to determine whether a metal will react with an acid or not. Write the balanced chemical reaction, including state variables, for each of the following reactions. For those metals that don’t react, write “No reaction”. (5 marks)

    • Dilute nitric acid and copper metal:

      (Copper is below hydrogen in the standard activity series for H₂ displacement, but nitric acid is an oxidizing acid and reacts differently.)

      3Cu(s) + 8HNO₃(aq) → 3Cu(NO₃)₂(aq) + 2NO(g) + 4H₂O(l)

    • Dilute phosphoric acid and magnesium metal:

      3Mg(s) + 2H₃PO₄(aq) → Mg₃(PO₄)₂(s) + 3H₂(g)

    • Dilute sulfuric acid and aluminium metal:

      2Al(s) + 3H₂SO₄(aq) → Al₂(SO₄)₃(aq) + 3H₂(g)

  6. During your investigation, you examined three metals: zinc, magnesium and aluminium. You may have noticed that one of your results conflicted with the Metal Activity Table. (4 marks)

    • Identify the metal that did not behave as predicted by the metal activity table.

      Aluminium (Al).

    • Speculate as to why this was the case.

      Aluminium is higher in the activity series than zinc and is expected to react with acids. However, our experiment showed no reaction. This is likely because aluminum readily forms a very thin, strong, and unreactive protective layer of aluminum oxide (Al₂O₃) on its surface when exposed to air. This oxide layer prevents the acid from coming into contact with the pure aluminum metal underneath, thus inhibiting the reaction.

    • Suggest an improvement to the experiment that may solve this paradox.

      To potentially observe the expected reaction, the protective oxide layer on the aluminum needs to be removed or breached. An improvement could be to: Thoroughly abrade the surface of the aluminum strip with sandpaper immediately before placing it into the acid. This would expose fresh, unoxidized aluminum metal to the acid. Alternatively, gently warming the acid (with appropriate safety precautions) might also help to initiate the reaction by slowly dissolving the oxide layer, but mechanical abrasion is a more direct method to test this hypothesis.

  • Get 100%, Your’s truly, kmaba.