Strong and weak acids and bases
Introduced| English | Meaning |
|---|---|
| concentration/ˌkɒnsənˈtreɪʃn/ | The amount of a substance per unit volume of a mixture or solution. |
| dissociated/dɪˈsəʊsɪeɪtɪd/ | Split into ions in solution. |
| strong acid/strɒŋ ˈæsɪd/ | An acid that essentially completely ionises in aqueous solution at the concentrations being considered. |
| weak acid/wiːk ˈæsɪd/ | An acid that only partially ionises in aqueous solution. |
| conductivity/kɒndəkˈtɪvɪti/ | conductivity |
How fully does it split?
- "Strong" and "weak" are about how fully an acid splits up in water.
- This is not the same as concentration 浓度.
- The pH scale measures how acidic a solution is.
"Strong" versus "weak" describes:
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Strength is about the degree of dissociation; concentration is a separate idea.
A weak acid only partially ionises in water.
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A strong acid fully ionises.
Fully vs partly dissociated 解离
- a strong acid 强酸/base is fully dissociated in water (almost every molecule splits into ions).
- a weak acid 弱酸/base is only partly dissociated (most molecules stay whole).
A strong acid is fully dissociated; a weak acid is only partly dissociated
Strong vs weak acids
A strong acid fully ionises (low pH); a weak acid only partly ionises, so at the same concentration its pH is higher. Slide to compare.
A strong acid is one that is:
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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 电导率 (more ions).
On the pH scale:
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Pure water is 7; acids are below 7 and alkalis above 7.
A strong acid conducts electricity better than a weak acid of the same concentration because it:
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Full dissociation gives more ions, so a strong acid conducts better and fizzes faster with metals.
Match each term to its meaning.
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Each item links the term to its correct meaning.
Strong is not concentrated
- Strong/weak describes how fully an acid ionises; concentrated/dilute describes how much is dissolved.
- A weak acid can be concentrated, and a strong acid dilute.
You've got it
- 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)