Question

1. Suppose that someone gives you an unknown solution, and you wish to find out whether this solution contains glucose. To do this, you perform a Benedict’s test.

1. Performing this test requires adding something called ____________________ solution to the solution of interest.

2. Consider the solution you named in the previous question. After adding this to your solution of interest, what do you have to do next?

3. If you perform a Benedict’s test on a solution that does contain glucose, then it would produce what color(s)?

4. If you perform a Benedict’s test on a solution that does not contain glucose, then what would you expect to see?

Suppose that you place glucose solution inside of a dialysis tube. You then place this tube in a beaker of water. Next, you let the dialysis tube sit in the beaker for an hour. Explain how you could figure out whether the glucose diffused out of the dialysis tube. Hint: Use your answers to parts a-e above

Answer 1

1. Suppose that someone gives you an unknown solution, and you wish to find out whether this solution contains glucose. To do this, you perform a Benedict’s test.

1. Performing this test requires adding something called Benedict's solution to the solution of interest.

1. Consider the solution you named in the previous question. After adding this to your solution of interest, what do you have to do next?

Keep the tube containing the mixture ( your solution + benedict's solution) in a hot water bath so that heat can catalyse the reaction.

1. If you perform a Benedict’s test on a solution that does contain glucose, then it would produce what color(s)?

The Benedict's solution is blue in color and when it is added to the solution being tested the resulting mixture will have blue color. When this mixture is heated depending on the concentration of glucose (or reducing sugars) the color varies from green, yellow orange to rust red. Rust red fomation happens at high amount of reducing sugar and greeen color at low amount of reducing sugar.

1. If you perform a Benedict’s test on a solution that does not contain glucose, then what would you expect to see?

If that solution does not contain glucose (or any other reducing sugar) then the color of the mixture remains the same (that is , blue).

Suppose that you place glucose solution inside of a dialysis tube. You then place this tube in a beaker of water. Next, you let the dialysis tube sit in the beaker for an hour. Explain how you could figure out whether the glucose diffused out of the dialysis tube. Hint: Use your answers to parts a-e above

Take out 1 ml of water in the begining of dialysis ( zero hour) and 1 ml of water after dialysis (1 hour) from the beaker in two different test tubes. Add 1 ml Benedicts solution to each test tube. Keep the test tubes in hot water bath and observe the color change. There will be no color change in the zero hour test tube and there will be color change in the 1 hour test tube since the latter has glucose in it.