Give reasons for the following: 1. Concentrated sulphuric acid is a weaker acid compared to dilute sulphuric acid. 2. An aqueous solution of the salt ammonium chloride is acidic in nature while an aqueous solution if sodium chloride is neutral. 3. Iron(III) chloride is stored in air tight bottles. 4. Acetic acid does not form an acid salt but forms a normal salt. 5. Sulphurous acid forms two types of salts in reaction with an alkali.



As acid strength depends on the relative amount of disassociation, then the a higher proportion of the dilute will disassociate, whereas , a smaller proportion would disassociate in the concentrated solution. 

Acid strength doesn't necessarily correlate with a solutions acidity, but it always correlates to the amount of acid which disassociates.

in concentrated H2SO4, H-S-O bonds are very strong, but when it reacts with water it forms H+ ions and dissociates.
i have no idea about the second one