Q2
1 markMCQSection A

Which of the given option represents a family of salts ?

Acids, Bases and Salts
Family of Salts

Options

(A)NaCl, Na2SO4Na_2SO_4, CaSO4CaSO_4
(B)K2SO4K_2SO_4, Na2SO4Na_2SO_4, CaSO4CaSO_4
(C)NaNO3NaNO_3, CaCO3CaCO_3, Na2CO3Na_2CO_3
(D)MgSO4MgSO_4, CuSO4CuSO_4, MgCl2MgCl_2
Official Answer

Option (B) — K2SO4K_2SO_4, Na2SO4Na_2SO_4, CaSO4CaSO_4 represents a family of salts.


As explained in the NCERT text (Activity 2.13, Section 2.4.1): "Salts having the same positive or negative radicals are said to belong to a family." Example given in the book: NaCl and Na2SO4Na_2SO_4 belong to the family of sodium salts; NaCl and KCl belong to the family of chloride salts.


In option (B), all three salts — potassium sulphate, sodium sulphate and calcium sulphate — contain the same negative (acid) radical, the sulphate ion SO42−SO_4^{2-}, even though their positive (basic) radicals (K+K^+, Na+Na^+, Ca2+Ca^{2+}) are different. Hence they belong to the sulphate family of salts.

Marking Scheme

  • 11 mark for correctly identifying option (B) with the common SO42−SO_4^{2-} radical reasoning.

Hint

Salts belonging to the same family share the same positive OR the same negative (acid) radical. Look for the common ion across all three salts in each option.

Quick Oral Answer

A family of salts is a set of salts sharing either the same cation or the same anion; K2SO4K_2SO_4, Na2SO4Na_2SO_4 and CaSO4CaSO_4 all share the sulphate ion SO42−SO_4^{2-}, making them the sulphate family.

Analysis & Explanation

A 'family of salts' (per the NCERT chapter) is a group of salts that share a common positive radical (cation) or a common negative radical (anion).


  • (A) NaCl, Na2SO4Na_2SO_4, CaSO4CaSO_4: NaCl has Cl−Cl^- as its negative radical while Na2SO4Na_2SO_4 and CaSO4CaSO_4 have SO42−SO_4^{2-}; NaCl and Na2SO4Na_2SO_4 share Na+Na^+, but CaSO4CaSO_4 shares neither the cation nor the anion with NaCl — so all three do not form one common family. Incorrect.
  • (B) K2SO4K_2SO_4, Na2SO4Na_2SO_4, CaSO4CaSO_4: All three have the identical acid radical SO42−SO_4^{2-} (potassium sulphate, sodium sulphate, calcium sulphate), so they belong to the sulphate family. Correct.
  • (C) NaNO3NaNO_3, CaCO3CaCO_3, Na2CO3Na_2CO_3: NaNO3NaNO_3 has NO3−NO_3^- while CaCO3CaCO_3 and Na2CO3Na_2CO_3 have CO32−CO_3^{2-} — the negative radicals are not common to all three, and only two of them share Na+Na^+. Incorrect.
  • (D) MgSO4MgSO_4, CuSO4CuSO_4, MgCl2MgCl_2: MgSO4MgSO_4 and CuSO4CuSO_4 share SO42−SO_4^{2-}, but MgCl2MgCl_2 has Cl−Cl^- instead; only MgSO4MgSO_4 and MgCl2MgCl_2 share Mg2+Mg^{2+} — no single radical is common to all three. Incorrect.

Common Mistakes

  1. 1Assuming any three salts of common everyday substances form a 'family' without checking that ALL of them share one common radical.
  2. 2Confusing 'family' (same radical) with salts simply being 'related' because they contain a common element like sodium somewhere.

Interesting Facts

The same logic used for a 'family of salts' also explains the periodic-table-like grouping used in qualitative salt analysis, where sulphates, chlorides, carbonates etc. are tested as separate radical groups.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2025?

This question carries 1 mark in the CBSE Class 10 Science 2025 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Acids, Bases and Salts" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Family of Salts" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2025 paper?

This is a MCQ question from Section A in the CBSE Class 10 Science 2025 paper.