Question

в двух пронумерованных пробирках находятся водные растворы сахарозы и глюкозы.составьте план распознания веществ.напишите уравнение реакций,при помощи которых можно идентифицировать данные вещества.

Answer 1

1. В качестве реактива приготовить Cu(OH)2:
СuSO4+ 2NaOH---> Cu(OH)2+ Na2SO4 
2/ В каждую пробирку добавить свежеосаждённый гидроксид меди. В обеих появится васильковый цвет:
2C6H12O6+ Cu(OH)2---> (C6H11O6)2Cu+2H2O

2C12H22011+2Cu(OH)2---> (C12H21011)2Cu+2H2O

3) Затем нагреть обе пробирки. В пробирке с сахарозой ничего не произойдет. Пробирка с глюкозой покраснеет:
СH2OH-(CHOH)4-COH+2Cu(OH)2----> CH2OH-(CHOH)4-COOH+ Cu2O+2H2O 

Answer 2

Plan for Substance Identification:

To identify the substances in the two labeled test tubes containing aqueous solutions of sucrose and glucose, we can follow the following plan:

1. Observation: Observe the physical properties of the solutions in the test tubes, such as color, transparency, and odor.

2. Chemical Tests: Perform specific chemical tests to identify the presence of sucrose and glucose in the solutions. The following tests can be conducted:

a. Benedict's Test: Benedict's reagent can be used to test for the presence of reducing sugars, such as glucose. The test involves heating the solution with Benedict's reagent, which will result in a color change if reducing sugars are present.

b. Fehling's Test: Fehling's solution can also be used to test for the presence of reducing sugars. The test involves heating the solution with Fehling's solution, which will result in a color change if reducing sugars are present.

c. Tollens' Test: Tollens' reagent can be used to test for the presence of reducing sugars, such as glucose. The test involves mixing the solution with Tollens' reagent and heating it, which will result in the formation of a silver mirror if reducing sugars are present.

d. Molisch's Test: Molisch's reagent can be used to test for the presence of carbohydrates, including sucrose and glucose. The test involves adding Molisch's reagent to the solution, followed by the addition of concentrated sulfuric acid. A purple ring or color change indicates the presence of carbohydrates.

e. Hydrolysis Test: Hydrolysis can be performed to break down sucrose into its constituent monosaccharides, glucose, and fructose. This can be achieved by adding dilute acid or enzyme invertase to the solution and heating it. The resulting solution can then be tested for the presence of glucose using the above-mentioned tests.

3. Comparison: Compare the results of the chemical tests with known reactions and color changes associated with sucrose and glucose to confirm the presence of these substances in the respective test tubes.

Equations for Reactions:

Here are the equations for the reactions involved in the chemical tests mentioned above:

1. Benedict's Test: ``` Glucose + Cu2+ (in Benedict's reagent) → Glucose oxidation + Cu2+ reduction Result: Formation of a colored precipitate (red, orange, or yellow) indicates the presence of reducing sugars like glucose. ```

2. Fehling's Test: ``` Glucose + Cu2+ (in Fehling's solution) → Glucose oxidation + Cu2+ reduction Result: Formation of a colored precipitate (red, orange, or yellow) indicates the presence of reducing sugars like glucose. ```

3. Tollens' Test: ``` Glucose + Ag+ (in Tollens' reagent) → Glucose oxidation + Ag+ reduction Result: Formation of a silver mirror on the inner surface of the test tube indicates the presence of reducing sugars like glucose. ```

4. Molisch's Test: ``` Carbohydrates + Molisch's reagent → Formation of a complex compound Result: Formation of a purple ring or color change indicates the presence of carbohydrates like sucrose and glucose. ```

Please note that the hydrolysis of sucrose into glucose and fructose involves the breakdown of the glycosidic bond between the two monosaccharides. The specific reaction conditions and equations may vary depending on the method used for hydrolysis.

Remember to perform these tests in a controlled laboratory environment and follow appropriate safety precautions.