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The following weak acids are used in the food industry - VCE - SSCE Chemistry - Question 3 - 2012 - Paper 1
Question 3
The following weak acids are used in the food industry. **Sorbic Acid** Common use: preservative Formula: C₆H₈O₂ Kₐ value: 1.73 × 10⁻⁵ **Malic Acid** Com... show full transcript
Worked Solution & Example Answer:The following weak acids are used in the food industry - VCE - SSCE Chemistry - Question 3 - 2012 - Paper 1
Step 1
What does the term ‘weak acid’ mean?
Answer
A 'weak acid' refers to an acid that does not completely ionize in water. This implies that in a dilute aqueous solution, only a fraction of the acid molecules dissociate to share protons (H⁺ ions) with water, leading to a higher pH compared to strong acids that fully ionize. Consequently, weak acids exist in equilibrium between their ionized and unionized forms in solution.
Step 2
Why are two Kₐ values listed for malic acid?
Answer
Malic acid is classified as a diprotic acid, meaning it can donate two protons (H⁺ ions) during its ionization process. The two Kₐ values correspond to the two distinct stages of this ionization: the first Kₐ represents the dissociation of the first proton, while the second Kₐ indicates the dissociation of the second proton, reflecting the two-step ionization process.
Step 3