How can I diffentiate between strong acid and weak base
Answers
Answer:
Weak” means when you dissolve it in water that not all of it dissociates into its ions.
“Strong” means 100% of the acid or base dissociates into its ions when you dissolve it in water.
for example, a 1M solution of acetic acid in water will only dissociate about 5%. that means 95% dissolves but remains as CH3COOHCH3COOH. Only 5% of the original amount becomes CH3COO−CH3COO− and H+H+ in water.
Similarly, if you make a 1M solution of HClHCl, then 100% of it will dissociate into H+H+ and Cl−Cl−.
Similarly for bases, NaOHNaOH is strong and fully dissociates in water into Na+Na+ and OH−OH− whereas ammonia, NH3NH3, is weak and only a small fraction of it becomes ammonium, NH+4NH4+, and hydroxide ions, OH−OH−.
All of this discussion works in concentration ranges we typically work with in the lab. about 1 molar to .01 molar.
if the concentration is very high then even HCl is not going to dissociate because of LeChatelier’s principle.
If the concentration is very low then even acetic acid and ammonia will ionize 100% again, because of LeChatelier’s principle.
Thus, a better way to describe acids and bases that works for all concentration ranges is to use the equilibrium constants for the dissolution of the species. for an acid, we use Ka or more compactly, pKa. small pKa values mean stronger acids and larger pKa values mean weaker acids.
for bases, we use Kb values or again, pKb. small pKb values mean stronger bases and larger pKb values mean weaker bases.