Strong and weak acids and bases
Strong and weak acids
- "Strong" and "weak" are about how fully an acid splits up in water.
- This is not the same as concentration.
- The pH scale measures how acidic a solution is.
Practice
"Strong" versus "weak" describes:
Strength is about the degree of dissociation; concentration is a separate idea.
Fully vs partly dissociated
- a strong acid/base is fully dissociated in water (almost every molecule splits into ions).
- a weak acid/base is only partly dissociated (most molecules stay whole).
Practice
A strong acid is one that is:
A strong acid splits up almost completely into ions; a weak acid only partly dissociates.
pH and telling them apart
- The pH scale: pure water is 7, acids below 7, alkalis above 7.
- A strong acid has a lower pH than a weak acid of the same concentration.
- Tell them apart by: faster fizzing with a reactive metal, lower pH, and better conductivity (more ions).
Practice
On the pH scale:
Pure water is 7; acids are below 7 and alkalis above 7.
Practice
A strong acid conducts electricity better than a weak acid of the same concentration because it:
Full dissociation gives more ions, so a strong acid conducts better and fizzes faster with metals.
You've got it
Key idea
- strong = fully dissociated; weak = partly dissociated (this is about dissociation, not concentration)
- pH: 7 neutral, <7 acid, >7 alkali; a strong acid has a lower pH than a weak one (same concentration)
- distinguish by metal fizz, pH, and conductivity (strong acid = more ions → conducts better)