what is difference between dilute and concentrated acids?
Basically the terms dilute and concentrated are used in reference to the amount of a solute that is dissolved in a given quantity of solvent. In dilute solutions, the amount of solute is less while that of solvent is more. On the other hand in concentrated solutions, the amount of solute is more while that of solvent is less.
So, concentrated acids are those in which have more amount of acid and less amount of water. The number of H+ ions in such solution is also high. Conversely, dilute acids are those in which amount of acid is less, but water is more. The number of H+ ions in such solutions is low.
The concentrated acid are the acid which has hundred percent of acid content in it (ideally little water is always present) and the dilute acid is when you add the solvent to the acid (water) you dilute the acid. The more solvent you add more dilute the acid becomes. The precautions should be taken while working with con. acids.