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Chapter 1: Problem 1

Which of the statements about the reaction below are incorrect? \(2 \mathrm{PbO}(\mathrm{s})+\mathrm{C}(\mathrm{s}) \rightarrow 2 \mathrm{~Pb}(\mathrm{~s})+\mathrm{CO}_{2}(\mathrm{~g})\) (a) Lead is getting reduced. (b) Carbon dioxide is getting oxidised. (c) Carbon is getting oxidised. (d) Lead oxide is getting reduced. (i) (a) and (b) (ii) \(\quad\) (a) and (c) (iii) \((\mathrm{a}),(\mathrm{b})\) and \((\mathrm{c})\) (iv) all

Short Answer

Expert verified
(b) is incorrect.

Step by step solution

01

Identify Oxidation and Reduction

Oxidation involves the loss of electrons, whereas reduction involves the gain of electrons. In the reaction, PbO turns into Pb, meaning lead is gaining electrons (getting reduced). Carbon turns into CO2, meaning carbon is losing electrons (getting oxidized).
02

Analyze Statement (a)

Statement (a) says 'Lead is getting reduced.' Since PbO is converting to Pb, lead is indeed getting reduced. Therefore, statement (a) is correct.
03

Analyze Statement (b)

Statement (b) says 'Carbon dioxide is getting oxidized.' In the reaction, CO2 is a product and does not undergo further oxidation or reduction. So statement (b) is incorrect.
04

Analyze Statement (c)

Statement (c) says 'Carbon is getting oxidized.' Since carbon is turning into CO2 by losing electrons, carbon is indeed getting oxidized. Therefore, statement (c) is correct.
05

Analyze Statement (d)

Statement (d) says 'Lead oxide is getting reduced.' Since PbO is turning into Pb, PbO is indeed getting reduced. Therefore, statement (d) is correct.
06

Identify Incorrect Statements

Based on the analysis, the incorrect statement is (b). Considering the given options, the correct answer is (i) (a) and (b), since statement (b) is incorrect, and statement (a) is not incorrect.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Oxidation
In chemistry, oxidation refers to a process where an atom, ion, or molecule loses electrons. This doesn't necessarily need to involve oxygen, though the name has historical roots from reactions involving oxygen. For instance, in the provided reaction, carbon is oxidized because it loses electrons.

Here's what happens step-by-step:
  • Carbon reacts with lead(II) oxide (PbO).
  • In this process, carbon loses electrons and forms carbon dioxide (CO2).

Losing electrons means the oxidation state of carbon increases. Initially, carbon has an oxidation state of 0, but in CO2, it becomes +4. Remember, loss of electrons always increases the oxidation state.
Reduction
Reduction is the opposite of oxidation. It involves the gain of electrons by an atom, ion, or molecule. In the given reaction, lead(II) oxide (PbO) undergoes reduction.

Let's break it down:
  • Initially, lead in lead(II) oxide (PbO) has an oxidation state of +2.
  • During the reaction, PbO transforms into lead (Pb).
  • In this process, lead gains electrons, reducing its oxidation state from +2 to 0.

This gain of electrons is what defines the reduction process. So, when lead oxide (PbO) gains electrons and turns into lead (Pb), it is getting reduced.
Electron Transfer
Electron transfer is a core concept in both oxidation and reduction reactions. These reactions are often called redox reactions, where one species loses electrons and another gains them.

In the given reaction:
  • Carbon loses electrons (oxidation) and forms CO2.
  • PbO gains those electrons (reduction) and turns into Pb.

This transfer of electrons is the essence of the redox process. During this transfer:
  • Electrons move from the reducing agent (carbon) to the oxidizing agent (PbO).
  • The reducing agent loses electrons - it is oxidized.
  • The oxidizing agent gains electrons - it is reduced.

Understanding electron transfer helps in identifying which substances are oxidized and which are reduced in any given reaction.

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Most popular questions from this chapter

Translate the following statements into chemical equations and then balance them. (a) Hydrogen gas combines with nitrogen to form ammonia. (b) Hydrogen sulphide gas burns in air to give water and sulpur dioxide. (c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate. (d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

Balance the following chemical equations. (a) \(\mathrm{HNO}_{3}+\mathrm{Ca}(\mathrm{OH})_{2} \rightarrow \mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{H}_{2} \mathrm{O}\) (b) \(\mathrm{NaOH}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}+\mathrm{H}_{2} \mathrm{O}\) (c) \(\mathrm{NaCl}+\mathrm{AgNO}_{3} \rightarrow \mathrm{AgCl}+\mathrm{NaNO}_{3}\) (d) \(\mathrm{BaCl}_{2}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{BaSO}_{4}+\mathrm{HCl}\)

What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer. (a) Hydrogen gas and iron chloride are produced. (b) Chlorine gas and iron hydroxide are produced. (c) No reaction takes place. (d) Iron salt and water are produced.

Explain the following terms with one example each. (a) Corrosion (b) Rancidity

Write the balanced chemical equations for the following reactions. (a) Calcium hydroxide + Carbon dioxide \(\rightarrow\) Calcium carbonate + Water (b) Zinc + Silver nitrate \(\rightarrow\) Zinc nitrate + Silver (c) Aluminium + Copper chloride \(\rightarrow\) Aluminium chloride + Copper (d) Barium chloride + Potassium sulphate \(\rightarrow\) Barium sulphate + Potassium chloride
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