2025 Lab Question With Detailed Answers (Practical 1)
1.Which one of the solutions is the positive control, and which one of the
solutions is the negative control for the Benedict's reaction?: In
Benedicts reaction the positive controls are starch, sucrose, glucose
and the unknown solution. The negative control in the reaction is the
distilled water.
2.Which contains more reducing sugars, potato juice or onion juice? How
do you know?: The onion juice contained more reducing sugars than the
potato juice because the onion juice solution turned a more greenish
color rather than the potato juice that stayed blue proving that it was a
negative control.
3.Which one of the solutions is the positive control, and which one of the
solutions is the negative control for the Iodine reaction?: In the Iodine
reaction the positive controls were the starch and the unknown
solutions. The negative control was the distilled water.
4.Which colors more intensely for the Iodine Reaction, onion juice or potato
juice? Why?: The potato juice has more change because it contained
more starch which was proven by the experiment. Both solutions
showed a positive control how- ever the potato juice was a more clear
yellowish blue, which showed the presence of more starch rather than
the onion juice that was more cloudy.
5.Which one of the solutions is the positive control, and which one of the
solutions is the negative control for the Biuret reaction?: In the Biuret
reaction the positive control is the protein solution and the negative
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, control was the distilled water.
6.Which contains more peptide bonds egg albumin or honey? How do
you know?: The egg albumin contained more peptide bonds because
the solution contained traces of a violey color while the honey stayed
a blue color.
7.Do free amino acids have peptide bonds?: Free amino acids do not
have peptide bonds because in the lab the solution stayed blue
showing that it was a negative control.
8.What do you conclude about the solubility of lipids in polar solvents such
as water compared to nonpolar solvents such as acetone?: Nonpolar
solvents such as acetone dissolved the oil while the polar solvents such
as water separted itself from the oil to sit on top of the water.
9.What happened when the emulsifier was added?: When the emulsifier
was added it create a mixed and cloudy solution.
10.Which one of the solutions is the positive control, and which one of the
solutions is the negative control for the Sudan IV reaction?: In the Sudan
IV reaction the positive controls are the lipid and salad oil. The negative
control is the distilled water.
11.Compare tubes 1 and 3 in the second experiment. What is the
distribution of the dye with respect to the separated water and oil?: In tube
1, the solution
turned a bright hot pink which showed a positive control but still showed
a slight separation between the water and oil. In tube 3 the solution
mixed well however the solution turned the solution into a clear pink
which showed a negative control.
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1.Which one of the solutions is the positive control, and which one of the
solutions is the negative control for the Benedict's reaction?: In
Benedicts reaction the positive controls are starch, sucrose, glucose
and the unknown solution. The negative control in the reaction is the
distilled water.
2.Which contains more reducing sugars, potato juice or onion juice? How
do you know?: The onion juice contained more reducing sugars than the
potato juice because the onion juice solution turned a more greenish
color rather than the potato juice that stayed blue proving that it was a
negative control.
3.Which one of the solutions is the positive control, and which one of the
solutions is the negative control for the Iodine reaction?: In the Iodine
reaction the positive controls were the starch and the unknown
solutions. The negative control was the distilled water.
4.Which colors more intensely for the Iodine Reaction, onion juice or potato
juice? Why?: The potato juice has more change because it contained
more starch which was proven by the experiment. Both solutions
showed a positive control how- ever the potato juice was a more clear
yellowish blue, which showed the presence of more starch rather than
the onion juice that was more cloudy.
5.Which one of the solutions is the positive control, and which one of the
solutions is the negative control for the Biuret reaction?: In the Biuret
reaction the positive control is the protein solution and the negative
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, control was the distilled water.
6.Which contains more peptide bonds egg albumin or honey? How do
you know?: The egg albumin contained more peptide bonds because
the solution contained traces of a violey color while the honey stayed
a blue color.
7.Do free amino acids have peptide bonds?: Free amino acids do not
have peptide bonds because in the lab the solution stayed blue
showing that it was a negative control.
8.What do you conclude about the solubility of lipids in polar solvents such
as water compared to nonpolar solvents such as acetone?: Nonpolar
solvents such as acetone dissolved the oil while the polar solvents such
as water separted itself from the oil to sit on top of the water.
9.What happened when the emulsifier was added?: When the emulsifier
was added it create a mixed and cloudy solution.
10.Which one of the solutions is the positive control, and which one of the
solutions is the negative control for the Sudan IV reaction?: In the Sudan
IV reaction the positive controls are the lipid and salad oil. The negative
control is the distilled water.
11.Compare tubes 1 and 3 in the second experiment. What is the
distribution of the dye with respect to the separated water and oil?: In tube
1, the solution
turned a bright hot pink which showed a positive control but still showed
a slight separation between the water and oil. In tube 3 the solution
mixed well however the solution turned the solution into a clear pink
which showed a negative control.
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