Question

In making candy or sugar syrups, sucrose is boiled in water with a little acid, such as lemon juice. Why does the product mixture taste sweeter than the starting sucrose solution?

Short answer

Answer: The product mixture tastes sweeter due to the hydrolysis of sucrose into glucose and fructose, which are both sweeter than sucrose itself. The acid acts as a catalyst for this reaction, resulting in a syrup that has a more pronounced sweet taste.

Step-by-step solution

Understand the chemical components of the problem

We know that the solution contains sucrose (a disaccharide sugar), water, and a little bit of acid, such as lemon juice. We will consider how the components interact and react with each other during the boiling process.

Analyze the chemical reaction occurring during boiling

When sucrose is boiled with a little acid, it undergoes hydrolysis, a chemical reaction that involves the breaking down of the disaccharide into its component monosaccharides, glucose and fructose. The acid catalyzes this reaction.

Reaction equation

The hydrolysis of sucrose can be represented by the following equation: Sucrose + Water + Acid -> Glucose + Fructose

Sweetness of monosaccharides

Glucose and fructose are both monosaccharides and are known to be sweeter than sucrose. In fact, fructose is considered to be one of the sweetest natural sugars. The presence of glucose and fructose in the product mixture thus enhances the overall sweetness of the resulting syrup.

Conclusion

The product mixture after boiling the sucrose solution with a little acid tastes sweeter than the starting solution due to the hydrolysis of sucrose into glucose and fructose, which are both sweeter than sucrose itself. The acid acts as a catalyst for this reaction, resulting in a syrup that has a more pronounced sweet taste.