枣庄学院化学化工与材料科学学院 Preparation of Solution

枣庄学院化学化工与材料科学学院 1. Grasp the basic Method and Operation of Preparing Solution 2. Study the Method of Use about Volumetric Flask and Pipette 3. Review the Method of Weighing Purpose of Experiment

枣庄学院化学化工与材料科学学院 M ＝ n/V (M: molarity of solution) When diluting solution, the amount of solute is constant. M 1 V 1 ＝ M 2 V 2 Principle of Experiment

枣庄学院化学化工与材料科学学院 Classification of Preparing Solution （ 1 ） rough preparation ： feature ： approximate concentration ， used for qualitative experiments instruments: table balance, graduated cylinder, beaker, stirring rod （ 2 ） accurate preparation ： feature ： accurate concentration ， used for quantitative experiments Instruments: electric balance, pipette, beaker, volumetric flask, stirring rod

枣庄学院化学化工与材料科学学院 Introduction of Volumetric Flask ● It is pear-shaped, long-stem, with the flat bottom. ● It is fitted with a glass stopper. ● There is a marked line on the neck.

枣庄学院化学化工与材料科学学院 Introduction of Volumetric Flask ● Volumetric flask is used to prepare a chemical solution with accurate concentration. ● There is a label on the flask with a temperature (usually 20 ℃ ) and volume. ● Various sizes: 25mL, 50mL, 100mL, 250mL, 500mL and 1000mL.

枣庄学院化学化工与材料科学学院 How to Use Volumetric Flasks 1 、 check for leaks ： add some water into the flask near the marked line, then seal the stopper firmly by pressing it with your left hand and hold the bottom with your right, invert the flask about two minutes, check if it is leaky; rotate the stopper 180 degrees, repeat the operation and check again, if it is not leaky, it’s qualified. Because the stopper matches the flask, you must tie the stopper to the neck with elastic in order to avoid loss. It can’t be heated. 2 、 rinse ： rinse the flask with lotion and water, then with distilled water 2-3 times, until it meets standard. 3 、 fill with paper ： after completing the experiment, rinse again, and fill a piece of in flask mouth.

枣庄学院化学化工与材料科学学院 Introduction of Pipette A pipette is used to measure small amounts of solution very accurately. There is a bulb in the middle, and there is a label on the bulb with temperature and volume. There is a marked line on the pipette.

枣庄学院化学化工与材料科学学院 How to Use a Pipette ： 1. Rinse ： (1) Rinse the pipette with water and distilled water 2-3 times. (2) Draw the liquid to be measured to the half of the bulge of a pipette. Tilt and rotate the pipette slowly to moisten the inside surface with the liquid, and drain the liquid. (3) Use the pipette immediately after repeating the operation 2-3 times.

枣庄学院化学化工与材料科学学院 2. Draw the liquid ： (1) Insert the tip of the pipette into the liquid 1-2cm, squeeze the pipette bulb with left hand and put the bulb on the flat end of the pipette. (2) Release the bulb to pull solution into the pipette, draw solution in above the marked line 1-2 cm. Quickly, remove the pipette bulb and put your index finger on the end of the pipette.

枣庄学院化学化工与材料科学学院 2. Draw the liquid ： (3) Gently rotate and release the seal by your fingers until the level of the solution meniscus exactly reach the marked line, then press the end of pipette tightly. Adjust the meniscus of the liquid to the line by dropping the liquid after pulling out the tip of the pipette above the surface of the liquid in the container.

枣庄学院化学化工与材料科学学院

3. Drain the liquid ： Pull out the pipette from the liquid and dry the outside surface with filter paper. Tilt the container, keep the pipette perpendicularly and the tip touching the inside surface, allow the liquid to fall naturally into the container.

枣庄学院化学化工与材料科学学院 3. Drain the liquid ： After almost all the liquid has been drained, hold the pipette 10-15s, then pull out the pipette. The last droplet remaining in the tip doesn’t be blew into the container.

枣庄学院化学化工与材料科学学院

1 、 Accurate preparing 100ml 6mol·L -1 NaOH solution with solid NaOH. 2 、 Accurate preparing 250ml mol·L -1 HAc solution with mol·L -1 HAc solution 。 Content of Experiment

枣庄学院化学化工与材料科学学院 apparatus ： beaker, pipette, volumetric flask, weighing bottle, electric balance, stirring rod medicine ： NaOH, HAc(2.0000mol·L -1 ) distilled water Things You’ll Need

枣庄学院化学化工与材料科学学院 The method of preparing solution 1 、 Calculation ： calculate the mass or volume of solute required. 2 、 Weigh or measure ： weigh out the mass of solid solute required with electric balance or measure the volume of liquid solute with pipette. 3 、 Dissolve ： put the solid solute into the beaker, add less distilled water to dissolve it, stir the solution until the solute is dissolved completely.

枣庄学院化学化工与材料科学学院 4 、 Transfer ： Transfer the entire liquid from the beaker into the flask. Stirring rod is used for drainage. In order to transfer the entire solute in the beaker as well as on the stirring rod, wash them well with distilled water 2-3 times and transfer the rinsed liquid to the flask.  5 、 Add water and shake slightly ： Add more water into the flask until the volume of the solution reaches the 2/3 of total volume of the flask, shake the flask slightly, and continue adding distilled water below the marked line about 1cm, stop adding.

枣庄学院化学化工与材料科学学院

6 、 Dilute to graduation and mix thoroughly ： Move your eyes to the level of the marked line of the flask. add distilled water drop by drop with a medicine dropper till the bottom of meniscus matches with the marked line. Seal the stopper firmly by pressing it with your left hand and hold the bottom of flask with your right, then invert and turn the solution about 10 times in order to mix the solution thoroughly. 7 、 Bottling and labelling ： Pour the solution from flask into reagent bottle, and labelled.

枣庄学院化学化工与材料科学学院