Strong Acids & Weak Acids
This lesson covers:
- The differences between strong and weak acids
- The relationship between a solution's pH, and the concentration of hydrogen ions
- The difference between the terms 'strength' and 'concentration'
A substance which forms an aqueous solution with a pH of less than 7 is defined as:
An alkali
An acid
A base
A salt
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When acid molecules are added to water and split apart, we say that they 'ionise' or 'dissociate'. These two words both mean the same thing.
acids ionise completely, whereas acids only partially ionise.
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Which of the following substances are strong acids?
(Select all that apply)
Sulfuric acid
Ethanoic acid
Hydrochloric acid
Nitric acid
Citric acid
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True or false? The dissociation of weak acids is a reversible reaction, which means that the products can react together to reform the acid.
True
False
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For a weak acid, does the position of equilibrium lie to the left or the right?
Left
Right
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Which of the following substances are weak acids?
(Select all that apply)
Hydrochloric acid
Nitric acid
Carbonic acid
Ethanoic acid
Citric acid
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Carbonic acid is described as a weak acid.
Which of the following statements apply to carbonic acid?
(Select all that apply)
It will form a solution with a pH of less than 7
It does fully dissociate to release hydrogen ions
It does not fully ionise to release hydrogen ions
It will form a solution with a pH of more than 7
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Which of these describes the strength of an acid?
The proportion of acid molecules which dissociate into hydrogen ions
The number of hydrogen ions released by the acid molecule
The concentration of hydrogen ions in a solution
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The concentration of an acid refers to the number of moles of acid molecules per unit of volume.
For example, hydrochloric acid could be 2 mol/dm3, which would mean 2 moles of HCl molecules per dm3 of solution.
True or false? The strength of an acid is the same as its concentration.
True
False
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pH is a measure of the hydrogen ion (H+) concentration of the solution.
This is NOT always the same as the acid's concentration.
As the concentration of hydrogen ions in a solution increases, what happens to the pH?
The pH increases
The pH decreases
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A solution decreases from pH 6 to pH 5.
By what factor has the concentration of hydrogen ions increased?
10 x
100 x
1000 x
10,000 x
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