Qualitative Analysis of Carbohydrates - MeitY OLabs
Summary
TLDRThis script details a series of qualitative tests for carbohydrates, focusing on solubility and the presence of reducing sugars. Glucose, sucrose, and starch are tested for solubility in water, with glucose and sucrose dissolving completely, while starch remains insoluble. Molisch's, Fehling's, Benedict's, and Tollen's tests are performed to identify reducing sugars, with glucose producing positive results, indicating its reducing nature, while sucrose and starch show negative results. The iodine test confirms the presence of starch by turning blue.
Takeaways
- 🍬 Glucose is soluble in water and completely dissolves when mixed with distilled water.
- 🍭 Sucrose, like glucose, is also soluble in water and dissolves completely in distilled water.
- 🌾 Starch is insoluble in water and does not dissolve even when mixed with distilled water.
- 🧪 Molisch's test is used to identify the presence of carbohydrates, as indicated by a red-violet ring at the junction of two layers in all tested samples.
- 🔍 Fehling's test is used to detect reducing sugars, which was positive for glucose but negative for sucrose and starch.
- 🔥 Benedict's test also identifies reducing sugars, showing a positive result for glucose and negative for sucrose and starch.
- 🌀 Tollen's test is used to detect the presence of reducing sugars, which was only positive for glucose, indicating the formation of a silver mirror.
- 🌿 The iodine test is used to identify the presence of starch, which turns blue in the presence of iodine, confirming starch but not for glucose or sucrose.
- 📚 Glucose is identified as a reducing sugar in various tests due to its ability to reduce metal ions in the test reagents.
- 🚫 Sucrose and starch are identified as non-reducing sugars, as they do not cause a color change in tests designed for reducing sugars.
- 🔬 The script demonstrates various chemical tests for identifying the properties of different carbohydrates, highlighting their solubility and reactivity.
Q & A
What is the solubility of glucose in water as demonstrated in the script?
-Glucose completely dissolves in water as shown by adding 3ml of distilled water to it in a test tube and shaking well.
Does sucrose behave similarly to glucose in terms of solubility in water?
-Yes, sucrose also completely dissolves in water, as evidenced by the same procedure used for glucose.
How does starch differ from glucose and sucrose in its solubility in water?
-Starch is insoluble in water, unlike glucose and sucrose, which both dissolve completely.
What is the purpose of Molisch's test in the context of the script?
-Molisch's test is used to detect the presence of carbohydrates. It produces a red-violet ring at the junction of two layers when a carbohydrate is present.
What color change indicates the presence of a reducing sugar in the Fehling's test?
-In the Fehling's test, a deep blue color change followed by the formation of a red precipitate of copper (I) oxide indicates the presence of a reducing sugar.
Why does the Fehling's test result in a negative outcome for sucrose?
-The Fehling's test is negative for sucrose because it is a non-reducing sugar and does not reduce the Cu(II) ions in the test reagent to copper (I) oxide.
What is the significance of the Benedict's test in identifying reducing sugars?
-The Benedict's test is used to identify reducing sugars. A color change to red and the formation of a copper (I) oxide precipitate indicate the presence of a reducing sugar.
How does Tollen's test differentiate between reducing and non-reducing sugars?
-Tollen's test involves the reduction of silver ions to elemental silver, which forms a silver mirror on the inner surface of the vessel. This reaction only occurs with reducing sugars, so no change indicates a non-reducing sugar.
What is the iodine test used for in the script?
-The iodine test is used to detect the presence of starch. It turns the solution blue when starch is present.
Why do glucose and sucrose not show a color change with iodine solution in the script?
-Glucose and sucrose do not show a color change with iodine solution because they do not contain starch, which is the substance that reacts with iodine to produce a blue color.
What does the lack of a characteristic change in the Tollen's test for sucrose and starch indicate?
-The lack of a characteristic change in the Tollen's test for sucrose and starch indicates that they are non-reducing carbohydrates, as no silver mirror is formed.
Outlines
🧪 Carbohydrate Solubility and Identification Tests
This paragraph outlines the procedures and outcomes of various tests used to analyze carbohydrates. It begins with the solubility test for glucose, sucrose, and starch, demonstrating that glucose and sucrose dissolve in water while starch does not. The Molisch's Test is then conducted on glucose, sucrose, and starch, resulting in a red-violet ring at the junction of layers for all three, indicating the presence of carbohydrates. The Fehling's test is applied to glucose, which shows a positive result with the formation of a red precipitate of copper (I) oxide, confirming its reducing nature. However, when applied to sucrose, the test remains negative, indicating it as a non-reducing sugar.
🔍 Further Carbohydrate Tests: Benedict's and Tollen's
The second paragraph continues with the Benedict's Test, where glucose shows a positive result with a red precipitate of copper (I) oxide, while sucrose and starch tests remain negative, indicating no reducing sugars. The Tollen's Test is also described, with glucose producing a silver mirror on the inner surface of the vessel due to the reduction of silver ions, confirming its reducing properties. In contrast, sucrose and starch show no characteristic changes, indicating the absence of reducing carbohydrates.
🌐 Iodine Test for Starch Detection
The final paragraph describes the Iodine Test, where iodine solution is added to aqueous solutions of glucose and sucrose, showing no characteristic change, thus indicating the absence of starch. However, when iodine is added to a starch suspension, the solution turns blue, confirming the presence of starch.
Mindmap
Keywords
💡Carbohydrates
💡Solubility Test
💡Glucose
💡Sucrose
💡Starch
💡Molisch's Test
💡Fehling's Test
💡Benedict's Test
💡Tollen's Test
💡Iodine Test
Highlights
Glucose and sucrose both completely dissolve in water, while starch is insoluble.
Molisch's test produces a red violet ring with glucose, sucrose, and starch, indicating the presence of carbohydrates.
Fehling's test shows a positive result for glucose, indicating it is a reducing sugar that reduces Cu(II) ions to copper (I) oxide.
Fehling's test is negative for sucrose and starch, indicating they are non-reducing sugars and do not contain reducing sugar.
Benedict's test also gives a positive result for glucose, confirming its reducing sugar nature.
Benedict's test is negative for sucrose and starch, further confirming they are non-reducing sugars.
Tollen's test produces a silver mirror on the inner surface of the vessel with glucose, indicating its reducing sugar property.
Tollen's test shows no characteristic change with sucrose and starch, indicating the absence of reducing carbohydrates.
Iodine test turns the starch solution blue, indicating the presence of starch, while there is no change with glucose and sucrose solutions.
Glucose and sucrose solutions show no characteristic change with iodine test, indicating the absence of starch.
Different tests are used to differentiate between reducing and non-reducing sugars.
Molisch's test is effective in identifying the presence of carbohydrates in both soluble and insoluble forms.
Fehling's and Benedict's tests are specific for detecting reducing sugars like glucose.
Tollen's test is a qualitative method to confirm the presence of reducing sugars by the formation of a silver mirror.
Iodine test is a simple and direct way to detect the presence of starch.
The solubility of carbohydrates in water can be an initial indicator of their type.
A combination of tests is necessary to accurately identify and differentiate carbohydrates.
These tests provide valuable insights into the chemical properties and behavior of different carbohydrates.
The results of these tests have practical applications in various fields such as food science, biochemistry, and medicine.
Transcripts
Qualitative Analysis of Carbohydrates
Solubility Test
Glucose
Using a spatula, take a small quantity of glucose and put it in a test tube.
Take about 3ml of distilled water in a dropper.
Pour it into the test tube and shake the test tube well.
Glucose completely dissolves in water.
Sucrose
Using a spatula, take a small quantity of sucrose and put it in a test tube.
Take about 3ml of distilled water in a dropper.
Pour it into the test tube and shake the test tube well.
Sucrose completely dissolves in water.
Starch
Using a spatula, take a small quantity of starch and put it in a test tube.
Take about 3ml of distilled water in a dropper.
Pour it into the test tube and shake the test tube well.
Starch is insoluble in water.
Molisch's Test
Glucose
Take Molisch's reagent using a dropper.
Add about 6 drops of Molisch's reagent into a test tube containing 2ml aqueous solution
of glucose.
Using a dropper, take a few drops Conc.
Sulphuric acid.
Add it slowly along the side of the test tube, without mixing.
A red violet ring is produced at the junction of the two layers (acid layer and test layer)
indicating the presence of carbohydrates.
Sucrose
Take Molisch's reagent using a dropper.
Add about 6 drops of Molisch's reagent into a test tube containing 2ml aqueous solution
of sucrose.
Using a dropper, take few drops Conc.
Sulphuric acid.
Add it slowly along the side of the test tube, without mixing.
A red violet ring is produced at the junction of the two layers (acid layer and test layer)
indicating the presence of carbohydrates.
Starch
Take Molisch's reagent using a dropper.
Add about 6 drops of Molisch's reagent into a test tube containing 2ml suspension of starch.
Using a dropper, take few drops Conc.
Sulphuric acid.
Add it slowly along the side of the test tube, without mixing.
A red violet ring is produced at the junction of the two layers (acid layer and test layer)
indicating the presence of carbohydrates.
Fehling's test
Glucose
Take 2 ml of Fehling's solution A using a dropper.
Add it to 2ml aqueous solution of glucose taken in a test tube.
Then add 2ml of Fehling's solution B into the test tube.
The solution turns a deep blue colour.
Remove the test tube from the rack using a test tube holder.
Place it in a boiling water bath and heat for few minutes.
Glucose is a reducing sugar that reduces the Cu(II) ions in the test reagent to red precipitate
of copper (I) oxide.
Sucrose
Take 2 ml of Fehling's solution A using a dropper.
Add it to 2ml aqueous solution of sucrose taken in a test tube.
Then add 2ml of Fehling's solution B into the test tube.
The solution turns a deep blue colour.
Remove the test tube from the rack using a test tube holder.
Place it in a boiling water bath and heat it for few minutes.
The colour remains the same.
The test is negative, indicating that sucrose is a non-reducing sugar.
Starch
Take 2 ml of Fehling's solution A using a dropper.
Add it to 2ml suspension of starch taken in a test tube.
Then add 2ml of Fehling's solution B into the test tube.
The solution turns deep blue colour.
Remove the test tube from the rack using a test tube holder.
Place it in a boiling water bath and heat it for few minutes.
The colour remains the same.
The test is negative, indicating that starch does not contain reducing sugar.
Benedict's Test
Glucose
Take 2ml of Benedict's reagent in a dropper.
Add it to 2ml aqueous solution of glucose taken in a test tube.
The colour of the solution turns blue.
Remove the test tube from the rack using a test tube holder.
Place it in a boiling water bath and heat for few minutes.
Glucose is a reducing sugar that reduces the Cu(II) ions in the test reagent to red precipitate
of copper (I) oxide.
Sucrose
Take 2ml of Benedict's reagent in a dropper.
Add it to 2ml aqueous solution of sucrose taken in a test tube.
The colour of the solution turns blue.
Take the test tube using a test tube holder.
Place it in a boiling water bath and heat for few minutes.
The colour remains the same.
The test is negative, indicating that sucrose is a non-reducing sugar.
Starch Take 2ml of Benedict's reagent in a dropper.
Add it to 2ml suspension of starch taken in a test tube.
The colour of the solution turns blue.
Remove the test tube from the rack using a test tube holder.
Place it in a boiling water bath and heat for few minutes.
The colour remains the same.
The test is negative, indicating that starch does not contain reducing sugar.
Tollen's Test
Glucose
Take 2ml of Tollen's reagent using a dropper.
Add it to a test tube containing 2ml aqueous solution of glucose.
Remove the test tube from the rack using a test tube holder.
Place it in a boiling water bath and heat it for 10 min.
Glucose is a reducing sugar that reduces silver ions in the test reagent to elemental silver,
which is accumulated on the inner surface of the reaction vessel, producing a silver
mirror on the inner surface of the vessel.
Sucrose
Take 2ml of Tollen's reagent using a dropper.
Add it to a test tube containing 2ml aqueous solution of sucrose.
Remove the test tube from the rack using a test tube holder.
Place it in a boiling water bath and heat for 10 min.
There will be no characteristic change indicating the absence of reducing carbohydrate.
Starch Take 2ml of Tollen's reagent using a dropper.
Add it into a test tube containing 2ml suspension of starch.
Remove the test tube from the rack using a test tube holder.
Place it in a boiling water bath and heat for 10 min.
There will be no characteristic change, indicating the absence of reducing carbohydrate.
Iodine Test
Glucose
Take a few drops of iodine solution using a dropper.
Add 2 drops of iodine solution into a test tube containing 2ml aqueous solution of glucose.
There will be no characteristic change, indicating the absence of starch.
Sucrose
Take a few drops of iodine solution using a dropper.
Add 2 drops of iodine solution into a test tube containing 2ml aqueous solution of sucrose.
There will be no characteristic change, indicating the absence of starch.
Starch
Take a few drops of iodine solution using a dropper.
Add 2 drops of iodine solution into a test tube containing 2ml suspension of starch.
The colour of the solution turns blue, indicating the presence of starch.
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