Preparation of junior high school solution:

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

(1) Experimental supplies: tray balance, beaker, glass rod , medicine spoon, sodium chloride, measuring cylinder (10mL, 50mL), rubber tip dropper.

(2) Experimental steps:

① Calculation

According to the formula for calculating the solute mass fraction, calculate and prepare 50g of sodium chloride with a solute mass fraction of 6% The mass of sodium chloride required for the solution is: 50gx6%=3g, and the mass of water required is 50g-3g=47g.

②Weighing

Use a tray balance to weigh 3g of sodium chloride and pour it into a beaker.

③Measure

Consider the density of water to be approximately 1g/cm3, and use a 50mL graduated cylinder to measure 47mL of water (Thinking: Why not use a 10mL graduated cylinder? If you choose 10mL The measuring cylinder needs to be measured 5 times to get the required water, which will lead to an increase in error).

④Dissolution

Pour a certain amount of water into the beaker containing sodium chloride and stir with a glass rod to speed up the dissolution of sodium chloride.

⑤ Bottle and store

Put the prepared solution into a reagent bottle, cap and label the bottle, indicate the drug name and solute mass fraction, and put it in the reagent cabinet middle.

Preparation steps

General steps for preparing a solution with a certain solute mass fraction:

① Calculate, ② Weigh, ③ Measure, ④ Dissolve, ⑤ Install bottle preservation.

If you use a prepared concentrated solution to prepare a dilute solution, the steps are:

① Calculate, ② Measure, ③ Mix, ④ Bottle and store

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How to use the solution:

① How to pour the liquid reagent: Remove the bottle cap and place it upside down on the table (to avoid contamination of the medicine). The label should face the palm of your hand (to prevent residual liquid from flowing down and corroding the label). Pick up the reagent bottle, place the bottle mouth close to the edge of the test tube mouth, slowly inject the reagent, cover the bottle cap with the label facing outward, and put it back in place.

② Dropping method of liquid reagent:

Use of dropper: a. First drive out the air in the dropper, and then absorb the reagent

b. Drop When adding the reagent, keep the dropper hanging vertically above the mouth of the container for dripping

c. During use, always keep the rubber nipple up to avoid being corroded by the reagent

d. Dropping After use, wash the tube with water immediately (except for the dropper on the dropper bottle)

e. When using the dropper, the rubber tip must not be extended into the container or come into contact with the wall, otherwise it will cause reagent contamination.