Chemical Reactions and Equations Quiz

What do you observe when a magnesium ribbon is burnt in air?

• A bright white flame and white powder (magnesium oxide) are observed.
• A bright yellow flame and black smoke are produced.
• A blue flame and a gas are released.
• A dull red flame and no residue are observed.

Do you observe anything happening around the zinc granules when react with HCl ?

• Yes, the zinc granules are melting.
• Yes, the zinc granules are changing color.
• No, nothing is happening around the zinc granules.
• Yes, bubbles or fizzing may be observed around the zinc granules.

What do you observe when potassium iodide solution is added to lead nitrate solution?

• A clear solution remains unchanged.
• A red precipitate of lead(II) iodide forms.
• A gas is released during the reaction.
• A yellow precipitate of lead(II) iodide forms.

Is the chemical equation Fe + H2O → Fe3O4 + H2 balanced?

• Yes

• No

Why should a magnesium ribbon be cleaned before burning in air?

• A magnesium ribbon should be cleaned before burning in air to remove impurities that can hinder combustion.
• To enhance the color of the flame during combustion.
• To make the ribbon more flexible for handling.
• To increase the magnesium's weight before burning.

Write the balanced equations for the following chemical reactions: (i) Hydrogen + Chlorine → Hydrogen chloride (ii) Barium chloride + Aluminium sulfate → Barium sulfate + Aluminium chloride (iii) Sodium + Water → Sodium hydroxide + Hydrogen

• H2 + Cl2 → HCl; 3BaCl2 + Al2(SO4)3 → 2BaSO4 + 3AlCl3; 2Na + 2H2O → NaOH + H2

• H2 + Cl2 → 2HCl; 3BaCl2 + Al2(SO4)3 → 3BaSO4 + 2AlCl3; 2Na + 2H2O → 2NaOH + H2

• H2 + Cl2 → 2HCl; 3BaCl2 + Al(SO4)3 → 3BaSO4 + AlCl3; 2Na + H2O → NaOH + H2

• H2 + Cl2 → HCl; BaCl2 + Al2(SO4)3 → BaSO4 + AlCl3; Na + H2O → NaOH + H2

Write a balanced chemical equation with state symbols for the following reactions: (i) Solutions of barium chloride and sodium sulfate in water react to give insoluble barium sulfate and a solution of sodium chloride. (ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.

• BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq)

• NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

• BaCl2(s) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq)

• (i) BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq); (ii) NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

A solution of a substance ‘X’ is used for whitewashing. (i) Name the substance ‘X’ and write its formula. (ii) Write the reaction of the substance ‘X’ named in (i) above with water.

• Calcium hydroxide, Ca(OH)2; Reaction: CaO + H2O → Ca(OH)2

• Potassium hydroxide, KOH; Reaction: K2O + H2O → 2KOH

• Magnesium hydroxide, Mg(OH)2; Reaction: MgO + H2O → Mg(OH)2

• Sodium bicarbonate, NaHCO3; Reaction: NaHCO3 + H2O → NaOH + CO2

Why does the iron nail become brownish in color and the blue color of copper sulfate solution fade?

• The iron nail turns brown due to rusting without any chemical reaction.

• Copper sulfate loses its blue color because it evaporates in the air.

• The iron nail becomes brownish from exposure to sunlight, not a chemical reaction.

• The iron nail becomes brownish due to the formation of iron(II) sulfate, and the blue color of copper sulfate fades as copper is displaced and precipitated.

Why does the color of copper sulfate solution change when an iron nail is dipped in it?

• The color change occurs because of the temperature increase when the nail is added.

• The color changes due to a displacement reaction where iron displaces copper from copper sulfate, resulting in a color change.

• The color change is caused by the evaporation of water in the solution.

• The color changes due to the iron rusting in the solution.