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Why does starch change to blue black when iodine solution is added then heated yet glucose has no observable reaction?
This is because starch is composed of polymers of glucose. Long linear chains are amylose. Amylopectin is similar but contains a branch point about every 25th glucose or so. Amylose coils into a helical secondary structure resembling a tube with a hollow core. Certain molecules including fatty acids and iodine can lodge inside the core as already mentioned. The complex of iodine stuck inside the amylose coil produces a characteristic blue-black colour. The starch itself is not altered. Starch-iodine complex becomes unstable at temperatures above 35 °C. This complex in presence of an oxidizing agent the solution turns blue, in the presence of reducing agent, the blue color disappears because triiodide (I3−) ions break up into three iodide ions, disassembling the complex. So starch turns into glucose molecules. Therefore the blue black colour disappears. However, when it cools down again, then the glucose macromolecules bonded up together again in a long chain, becoming starch. That is why it tested positive for starch and turns back into blue-black colour.
What else can I help you with?
What is an observable reaction?
An observable reaction is a change that can be measured, detected, or witnessed during a chemical or physical process. This can include changes in color, temperature, precipitation, gas formation, or the release of light or sound. It provides evidence that a chemical reaction or a physical change has occurred.
What apparatus is used in titration?
A burette is typically used in titration to deliver a precise volume of a solution into another solution until the reaction reaches completion, as indicated by a color change or other observable change. The burette allows for the careful measurement of the volume of solution added during the titration process.
What colour does potato change to when Benedict solution is added?
Potato turns blue or purple when Benedict's solution is added, indicating the presence of reducing sugars such as glucose. This color change occurs due to the chemical reaction between the reducing sugars in the potato and the copper ions in the Benedict's solution.
How do you do a titration?
To perform a titration, you slowly add a solution of known concentration (titrant) to a solution of unknown concentration until a reaction is complete, as indicated by a color change or other observable change. The volume of titrant used is used to calculate the concentration of the unknown solution.
Glucose and I2KI inside the bag what color would be present in dialysis tubing bag experiment?
In the dialysis tubing bag experiment, if glucose and I2KI are present inside the bag, the color of the I2KI solution will turn blue-black due to the reaction of iodine with starch present in the glucose solution. This color change indicates the presence of glucose inside the bag.
What is the 2nd observable characteristic of a chemical reaction?
There are many observable characteristics of a chemical reaction. They are: change in temperature formation of a precipitate change in color formation of a gas formation of a new odor disappearance of a solid
Does benedict's solution need heating when testing for glucose?
Yes, Benedict's solution needs heating to test for glucose. Heating helps to facilitate the reaction between glucose and the copper ions in the Benedict's solution, resulting in a color change that indicates the presence of glucose.
What color does glucose indicator turn?
When a glucose indicator, such as Benedict's solution or Fehling's solution, is added to a solution containing glucose and heated, it undergoes a chemical reaction with the reducing sugar glucose. This reaction results in a color change from blue (in the case of Benedict's solution) or deep blue (in the case of Fehling's solution) to a brick-red or orange precipitate. This color change indicates the presence of glucose in the solution.
What is an observable reaction?
An observable reaction is a change that can be measured, detected, or witnessed during a chemical or physical process. This can include changes in color, temperature, precipitation, gas formation, or the release of light or sound. It provides evidence that a chemical reaction or a physical change has occurred.
How does tritation work?
Titration is a technique used to determine the concentration of a substance in a solution by reacting it with a solution of known concentration. A burette is used to carefully add the titrant (known solution) to the analyte (unknown solution) until the reaction reaches a specific endpoint, indicated by a color change or another observable change. The volume of titrant added is used to calculate the concentration of the analyte.
How does Benedicts solution work with sugar?
Benedict's solution is a chemical reagent used to test for the presence of reducing sugars, such as glucose. When heated with a reducing sugar, such as glucose, in the presence of an alkali (sodium carbonate), a redox reaction occurs, causing the blue color of the Benedict's solution to change to a brick-red precipitate of copper oxide. The intensity of the color change is proportional to the amount of reducing sugar present in the solution.
What apparatus is used in titration?
A burette is typically used in titration to deliver a precise volume of a solution into another solution until the reaction reaches completion, as indicated by a color change or other observable change. The burette allows for the careful measurement of the volume of solution added during the titration process.
What colour does potato change to when Benedict solution is added?
Potato turns blue or purple when Benedict's solution is added, indicating the presence of reducing sugars such as glucose. This color change occurs due to the chemical reaction between the reducing sugars in the potato and the copper ions in the Benedict's solution.
What happens if 40 glucose is suspended in 40 glucose?
When 40 grams of glucose is suspended in 40 grams of glucose, it creates a concentrated solution of glucose. Since both the solvent and solute are the same substance (glucose), there is no effective dilution or change in concentration; the solution remains essentially a saturated glucose solution. The physical properties may change slightly, but chemically, it remains the same compound. This scenario essentially results in a more viscous solution due to the increased concentration of glucose.
How do you do a titration?
To perform a titration, you slowly add a solution of known concentration (titrant) to a solution of unknown concentration until a reaction is complete, as indicated by a color change or other observable change. The volume of titrant used is used to calculate the concentration of the unknown solution.
Glucose and I2KI inside the bag what color would be present in dialysis tubing bag experiment?
In the dialysis tubing bag experiment, if glucose and I2KI are present inside the bag, the color of the I2KI solution will turn blue-black due to the reaction of iodine with starch present in the glucose solution. This color change indicates the presence of glucose inside the bag.
How do you describe titration?
Titration is a laboratory technique used to determine the concentration of a substance in a solution by slowly adding a reagent of known concentration until a reaction is completed. This reaction is typically indicated by a color change or other observable change. Titration is commonly used in chemistry for analyzing acids, bases, and other substances.
