Increasing order of their acidic strength propanoic acid,ethanoic acid,2-fluoroethanoic acid,2-chloroethanoic acid,dichloroethanoic acid
Also give reasion .
Solution:- propanoic acid<ethanoic acid<2-chloroethanoic acid<2- fluoroethanoic acid<dichloroethanoic acid when alkyl group keeps increasing, electron pushing effect increases, more tha alkyl group, more the electron pushing, and more stronger the carbon which is bonded with oxygen (in COOH) which thus makes it harder to release H+ ion, decreasing the acidity. That's why, propanoic acid is weaker than ethanoic acid and so on.
But when it comes to halogen attached acids, we should know that halogens have the property of "pulling electrons" rather than pushing, because halogens being electronegative. So the pull electrons from the carbon, making the carbon weak, making it easier for the H+ ion to release. That's why chloroethanoic acid is weaker than floroethanoic acid and so on. Remember, more it is easy to release H+ ions, more it is acidic.