✓ Board-verified↻ asked 3×
Science · 2023 · 2 marks
CBSE 2023 · Region 2 · Set 1 · Q21
What is observed when aqueous solutions of potassium iodide and lead nitrate are mixed together ? Name the type of reaction and write the chemical equation for the reaction that occurs.When copper powder is heated in a watch glass, a black substance is formed.(i)Why is this black substance formed ? Name it.(ii)How can this black substance be reversed to its original form ?
What is observed when aqueous solutions of potassium iodide and lead nitrate are mixed together ? Name the type of reaction and write the chemical equation for the reaction that occurs.
When copper powder is heated in a watch glass, a black substance is formed.
(i)
Why is this black substance formed ? Name it.
(ii)
How can this black substance be reversed to its original form ?
Marking-scheme solution
(a) • Yellow precipitate of lead iodide is formed.
Double displacement reaction / Precipitation reaction
\[\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}+2 \mathrm{KI} \longrightarrow \mathrm{PbI}_{2}+2 \mathrm{KNO}_{3}
\]
(b) (i) • Oxygen is added to copper / Copper is oxidised
copper oxide / CuO
(ii) By passing hydrogen gas over it Alternative answer
(i) \(\displaystyle 2 \mathrm{Cu}+\mathrm{O}_{2} \xrightarrow{\Delta} 2 \mathrm{CuO}\)
(ii) \(\displaystyle \mathrm{CuO}+\mathrm{H}_{2} \longrightarrow \mathrm{Cu}+\mathrm{H}_{2} \mathrm{O}\)
More from Chemical Reactions and Equations
- Copper powder is taken in a china dish and heated over a burner. Name the product formed and state its…2024 · asked 3×
- Why do we balance a chemical equation? Name and state the law that suggests the balancing of a chemical…2025 · asked 3×
- Which of the following is an example of a displacement reaction?2026 · asked 3×
- Define a double displacement reaction. Write the chemical equation of a double displacement reaction which is…2023 · asked 3×
- The balanced chemical equation showing reaction between quicklime and water is:2023 · asked 3×
- C 6 H 12 O 6(aq)+6 O 2( g) → 6 CO 2( g)+6 H 2 O (l). The above reaction is an example of -2026 · asked 3×
- Which one of the following reactions is different from the remaining three?2024 · asked 3×
- (i) While electrolysing water before passing the current some drops of an acid are added. Why? Name the gases…2023 · asked 3×
CBSE Class 10 Science past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.