Acids and Bases
Translate between particle behavior, pH evidence, and reaction quantities without confusing strength and concentration.
Acids and Bases
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Acid–base questions connect proton transfer, concentration, and a logarithmic scale
A Brønsted–Lowry acid donates H+; a base accepts H+. At 25°C, pH+pOH=14. Each pH unit represents a tenfold change in hydrogen-ion concentration.
Strength versus concentration
Strength is degree of ionization; concentration is amount of solute per volume.
Use evidence carefully
Indicators give ranges, conductivity reflects mobile ions, and pH alone does not identify a substance or guarantee safety.
Classify → compare powers of ten → use the reaction ratio
Problem: Compare pH 3 and pH 5.
Recognize: pH is logarithmic; the difference is 2 units.
Do it fast: 10²=100, so the pH 3 solution has 100 times greater [H⁺].
Why it works
This sequence handles conceptual, logarithmic, and neutralization questions without treating pH as an ordinary linear scale.
Five forms you should recognize
[H+]=10⁻⁴ M gives pH 4.
A one-unit pH decrease means ten times greater [H+].
H+ and OH− form water; remaining ions form a salt.
A weak acid partially ionizes; it can still be concentrated.
A weak acid/conjugate base pair resists large pH changes.
Check before you commit
- Treating pH as linear
- Calling every concentrated acid strong
- Assuming neutralization removes all ions
- Confusing endpoint and exact equivalence
- Forgetting solution volumes in titration
- Using pH alone to judge safety
Do you need the lesson-or just practice?
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Foundations
Build the core procedure with immediate explanations.
Core Practice
Use mixed forms with less scaffolding.
UPCAT-Style Transfer
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Acids and Bases FAQ
Is pH 2 twice as acidic as pH 4?
No. Its hydrogen-ion concentration is about 100 times greater.
Are weak acids harmless?
No. “Weak” describes ionization equilibrium, not concentration or safety.
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