Experimental activity 5-sodium chloride solution with fixed solute mass fraction

Experimental activity 5

Preparation of Sodium Chloride Solution with Certain Solute Mass Fraction

Purpose

1.Practice preparing a solution with a certain mass fraction of solute.

2.Deepen the understanding of the concept of mass fraction of solute.

[ Experimental supplies]

Tray balance, beaker, glass rod, medicine spoon, measuring cylinder, plastic tip dropper.

Sodium chloride, steamed monk water.

Experimental steps

1.Prepare a sodium chloride solution with a mass fraction of 6% .

(1) Calculation: the quality of sodium chloride and water required for 6% sodium chloride solution to prepare 50 g mass fraction

(2)Weighing: Weigh the required sodium chloride with a tray balance and put it into a beaker.

(3)Measure: Use a graduated cylinder to measure the required water (the density of water can be approximately regarded as 1 g/cm 3 ), and pour it into a beaker filled with sodium chloride.

(4)Dissolution: Stir with a glass rod to dissolve the sodium chloride.

The whole preparation process is shown in the figure below.

2.Prepare a sodium chloride solution with a mass fraction of 3% .

Prepare 50 g of 3% sodium chloride solution with a mass fraction of 6% sodium chloride solution (density of about 1.04 g/cm 3 ) .

(1) Calculation: the mass fraction required to prepare 50 g of a 3% sodium chloride solution is that the mass fraction of 6% sodium chloride solution and the quality of water

(2) Measure: Measure the required sodium chloride solution and water with a graduated cylinder, and pour them into a beaker.

(3) Mixing: Stir with a glass rod to make the solution evenly mixed.

3.Put the above two prepared sodium chloride solutions into reagent bottles respectively, cover the stoppers and label them (the label should include the name of the drug and the mass fraction of the solute in the solution), and put them in the reagent cabinet.

Question and communication

1.What precautions should be taken when weighing sodium chloride with a tray balance?

2.What should be paid attention to when measuring liquid with a graduated cylinder?

3.What is the significance of accurately preparing a solution with a certain solute mass fraction in practical applications? Please give an example.