Question

Statement 1: correct order of acidic strength is $C{H}_{3}C{H}_3>C{H}_2=C{H}_2>HC=Ch$
Statement 2:- C-H bond energy in ethene is more than ethane but less than ethyne.

• A. Statement 1 is true, Statement 2 is true and Statement 2 is correct explanation for Statement 1.
• B. Statement 1 is true, Statement 2 is true and Statement 2 is NOT the correct explanation for Statement 1.
• C. Statement 1 is true, Statement 2 is false
• D. Statement 1 isfalse, Statement 2 is true

Answer 1

Answer: (D)

Statement 1 isfalse, Statement 2 is true

Ethyne> Ethene >Ethane .

This can be explained with the Hydrogen donating tendency of hydrocarbon, carbon which is more electronegative will create high positive charge on hydrogen, hence that hydrocarbon will me most acidic.

• Ethyne is most acidic because it contains acidic hydrogen (hydrogen connected with sp hybridised carbon ) % S character is 50%,hence most electronegative .

Both the hydrogen atoms are identical and connected with carbon which is sp hybridised hence, Ethyne is most acidic.

• Ethene is less acidic than Ethene as the carbon containing hydrogen is sp2 hybridised (%s character is 33.3, hence less electronegative).

Four identical hydrogen connected with sp2 hybridised carbon,hence less acidic in nature.

• Ethane is least acidic because both the carbons are sp3 hybridised (%s character is 25%, hence least electronegative).

Six hydrogen is attached with sp3 hybridised carbon.

Hence A is false and R is true