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Class 10
Solutions to CBSE Sample Paper - Science Class 10

The table shown below gives information about four substances: A, B, C and D. 

Q 28 - compounds from the above given substances - Teachoo.jpg

Identify Ionic compounds from the above given substances. 

(A) A, B 

(B) B, C 

(C) A, B, D 

(D) A, C, D

 

Answer - 

Ionic compounds have 

  • High melting points
  • And they are poor conductors of electricity in solid state, but good conductors in liquid state

Why Ionic compounds conduct electricity in Liquid state but not in Solid state-01.jpg

From the options

  • B, C, D have high melting points
  • But substance D is poor conductor in both solid and liquid state. Hence, substance D is not ionic.
  • Thus, only B and C are ionic
  • Hence, compound B and C are ionic compounds.

So, the correct answer is (b)

 

Note : Ionic compounds are poor conductors of electricity in their solid state because movement of ions is not possible in the solid state. Ionic compounds in their liquid state are good conductors of electricity as the electrostatic forces of attraction between the oppositely charged ions are overcome due to the heat. Thus, the ions move freely and conduct electricity. 

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