Benedict's reagent is used for detecting reducing sugars because _________.

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The correct answer is: the copper ion in the reagent is oxidized as the sugar is reduced.

Benedict's reagent is a chemical solution commonly used to test for the presence of reducing sugars, such as glucose and fructose. It consists of copper sulfate, sodium citrate, and sodium carbonate.

In the presence of reducing sugars, which have free aldehyde or ketone groups, the copper(II) ion (Cu2+) in the Benedict's reagent is reduced to copper(I) oxide (Cu2O) or copper(I) hydroxide (Cu(OH)2). This reduction reaction causes a color change in the solution from its initial blue color to green, yellow, orange, or brick red, depending on the concentration of the reducing sugar.

Therefore, the statement "the copper ion in the reagent is oxidized as the sugar is reduced" is the correct explanation for why Benedict's reagent is used for detecting reducing sugars.

The correct answer is:

The copper ion in Benedict's reagent is oxidized as the sugar is reduced.

To understand why Benedict's reagent is used for detecting reducing sugars, we need to understand the principle behind it. Benedict's reagent is a solution containing copper sulfate, sodium citrate, and sodium carbonate. When a reducing sugar, such as glucose or fructose, is present in the solution, it reacts with the copper ions in the reagent.

In this reaction, the aldehyde group in the reducing sugar gets oxidized, while the copper ion gets reduced. As a result, a red precipitate of copper(I) oxide forms. The presence of this red precipitate indicates the presence of reducing sugars.

So, to summarize, Benedict's reagent is used for detecting reducing sugars because the copper ion in the reagent is oxidized as the sugar is reduced.