W3 July CS-S4A Chem KPT + Separation Techniques Revision

The picture below shows the arrangement of particles in hexane at two different temperatures. Hexane has a melting point of -95 ^oC and a boiling point of 70 ^oC.

What could the values of X and Y be?

• X = -100 ^oC, Y = 90 ^oC

• X = -50 ^oC, Y = 10 ^oC

• X = 0 ^oC, Y = 100 ^oC

• X = 10 ^oC, Y = -50 ^oC

A substance was heated until it melted, and allowed to cool. The temperature time graph of the substance during the cooling process was recorded as shown below.

Which statement is correct? Select all options that apply.

• Along PQ, the molecules lose kinetic energy.

• Along QR, the average distance between the molecules decreases.

• Along QR, the molecules gain kinetic energy.

• The average distance between the molecules is smaller at PQ than at RS.

A chromatogram was taken for samples of insecticides A, B and C to check if the strains of Chye Sim and Kailan being grown at a farm contained these insecticides. 

What conclusion can be drawn from the results of this chromatogram?

• Both the Chye Sim and Kailan samples contain insecticide C.

• Both the Chye Sim and Kailan samples contain insecticide B.

• Only the Chye Sim sample contains insecticide A.

• Both Chye Sim and Kailan do not contain any of the three insecticides at all.

Substance A is a white solid that is soluble in ethanol, insoluble in water, and has a boiling point of 87 ^oC. 

Briefly describe the steps you would take to obtain a pure and dry sample of substance A from a mixture of substance A and table salt.

A student conducted an experiment on copper(II) chloride crystals.

In this experiment, solid copper(II) chloride crystals were heated until molten copper(II) chloride was obtained. 

Using kinetic particle theory, explain the changes in the arrangement and movement of the particles in copper(II) chloride in this experiment.