Question 171 markMCQSection A

Assertion (A) : Different metals have different reactivities with water and dilute acids.

Reason (R) : Extraction of a metal from its ore depends on its position in the reactivity series.

Metals and Non-metals
Reactivity Series

Options

(A)Both (A) and (R) are true and (R) is the correct explanation of (A).
(B)Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(C)(A) is true, but (R) is false.
(D)(A) is false, but (R) is true.

Official answer

B

Answer keywords:reactivity seriesextraction of metalsreactivity with waterreactivity with acids

Marking scheme

  1. 1.1 Mark for selecting the correct option B.

Hint

Check if both statements are true individually. Then, ask if the method of extraction explains why metals react differently with water and acids.

Quick oral answer

Both statements are true, but the reason is not the correct explanation of the assertion. The reactivity of metals with water and acids is due to their electronic configuration and tendency to lose electrons, while extraction is an industrial application of this reactivity.

Common mistakes

  1. 1.Assuming that because both statements are related to the reactivity series, the reason must be the correct explanation.
  2. 2.Thinking that extraction of metals is the cause of their chemical reactivity rather than a consequence.

Analysis and explanation

  • Assertion (A) is true: Different metals show different reactivities with water and dilute acids. For example, sodium and potassium react violently with cold water, calcium reacts less violently, magnesium reacts with hot water, iron reacts with steam, and copper does not react with water or dilute hydrochloric acid.
  • Reason (R) is true: The extraction of a metal from its ore depends on its position in the reactivity series. Highly reactive metals are extracted by electrolysis, moderately reactive metals by reduction using carbon, and least reactive metals are found in their native state.
  • Connection: Although both statements are true, the reason does not explain why different metals have different reactivities with water and acids. The difference in reactivity is due to the varying ease with which metal atoms lose electrons to form positive ions, which is a fundamental chemical property. The extraction method is merely an application of this reactivity series, not its cause. Therefore, (R) is not the correct explanation of (A).

  • Option A is incorrect because (R) is not the correct explanation of (A).
  • Option C and Option D are incorrect because both statements are true.

Interesting facts

Sodium and potassium are so reactive that they react explosively with water and must be stored under kerosene oil to prevent accidental fires.

Question details

Q17 of 39 questions

Board
CBSE
Class
Class 10
Subject
Science
Year
2024
Section
Section A
Marks
1
Type
MCQ
Chapter
Metals and Non-metals
Topic
Reactivity Series
Bloom's level
Analyzing
Syllabus topic
Reactivity series of metals and its significance

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Frequently asked questions

How many marks does this question carry in CBSE Class 10 Science 2024?

This question carries 1 mark in the CBSE Class 10 Science 2024 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Metals and Non-metals" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Reactivity Series" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2024 paper?

This is a MCQ question from Section A in the CBSE Class 10 Science 2024 paper.