Question

Ms. Diksha, a science teacher gave different substances to three students. One

spatula full of copper sulphate was given to student 1, wheat flour was given to

student 2 and ink was given to student 3. Each student added the given sample

to water and stirred. Which of the following statements is incorrect about the

mixtures prepared by them?

a. Particles are not visible to the naked eye in case of mixtures obtained by

student 1 and student 3.

b. The path of light become visible in case of mixture obtained by student

1.

c. When passed through filter paper, particles of mixture obtained by

student 2 remain behind on the filter paper.

d. The particle of mixture obtained by student 3 are about 100 times bigger

than those of the mixture obtained by student 1.​

Answer 1

iron is more reactive than copper.iron can displace copper sulphate solution to produce iron sulphate and a brown deposit of copper on the other hand aluminium and zinc are more reactive than iron therefore iron cannot displace aluminium and zinc from Aluminium sulphate and zinc sulphate solution. the student will observe a brown deposit in test tube 2

Answer 2

The statement ‘the path of light becomes visible in case of the mixture obtained by student 1’ will be incorrect.

Given:

Student 1: Copper sulfate + Water

Student 2:  Wheat flour + Water

Student 3: Ink + Water

Solution:

• The composition of copper sulfate and water will give a true solution while the composition of wheat flour and water will be a suspension.
• When the ink is mixed with water it will result in a colloidal solution.
• The particle size in a true solution will be less than 1 nm.
• For a colloidal solution, the particle size range between 1 nm and 100 nm.
• In the case of suspension, particle size will be greater than 100 nm.
• We cannot see the particles of a true solution and colloidal solution because their size is below 100 nm.
• But in the case of a suspension, particles can be seen using the naked eye, as the size of particles is greater than 100 nm.
• Tidal effect is seen in colloidal solution, as the light can scatter through it.
• Due to the greater size of suspension particles, when we pass a suspension through a filter paper, the particles will remain on the filter paper.

Hence, Option (b) will be the incorrect statement.

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