The preparation of chemical solutions, please explain in detail

Calculating, weighing, dissolving, transferring, washing, volumetric, shaking, bottling and labeling.

Preparation method of each kind of chemical solution:

Preparation of ammonia

The ammonia we bought back has a concentration of 25%, and we want to use this ammonia stock solution to prepare 10% and 2% ammonia. 10% ammonia is made from 2 parts of 25% ammonia mixed with 5 parts of water; 2% ammonia is made by mixing 2 parts 25% ammonia with 25 parts water.

Ammonia mixed with borax

The "mixture of 2 parts of borax, 1 part of ammonia with a concentration of 10% and 20 parts of water" mentioned in the article refers to the need to add 2g of borax and 1ml of 10% ammonia to 20ml of water. Since we are used to clean stains, there are no precise requirements for the amount of chemicals to be used.

Preparation of hydrogen peroxide

The concentration of medical hydrogen peroxide is generally less than 3%, so we need to dilute the hydrogen peroxide with a concentration of 30%. We mix 1 part of 30% hydrogen peroxide stock solution with 10 parts of water to get a hydrogen peroxide solution with a concentration of about 3% that can be used to clean the interior.

Preparation of sparkling water

The concentration of baking soda for medical purposes is 2%-4%. We clean using 4% baking soda. 4% baking soda refers to 4g of sodium bicarbonate that needs to be added to 100ml of water, and netizens can increase or decrease the amount of chemicals in proportion to the amount of cleaning solution they want to prepare.

Since we are used to clean stains, there are no precise requirements for the amount of chemicals to be used.

The preparation steps of the solution are as follows:

1. Calculation: Calculate the mass of the solid solute or the volume of the liquid concentrated solution required for preparation. According to the amount of solution to be prepared, calculate the required solute mass and liquid volume, only accurate calculation, the concentration of the prepared solution can be determined, in order to ensure the accuracy of the test, experiment, and laboratory results.

2. Weighing: Weigh the solid mass with a tray or use a graduated cylinder (a pipette is used, but a graduated cylinder is generally used in middle school) to measure the volume of liquid. For the preparation of standard solutions, the required solute mass needs to be accurately weighed with an analytical balance.

3. Dissolve: dissolve or dilute the solute in a beaker and return to room temperature, if it cannot be completely dissolved, it can be heated appropriately and stirred with a glass rod.

4. Transfer: Carefully transfer the cooled solution in the Qishan beaker into a certain volume of Rongweiyou measuring flask along the glass rod, and the lower end of the glass rod should be leaning below the scale line of the volumetric flask.

5. Washing: Wash the beaker and glass rod 2 3 times with distilled water, and transfer the washing solution into the container, shake, and mix the solution evenly.

6. Constant volume: When adding water to the volumetric flask to 1cm 2cm below the scale line, use the rubber head dropper to add water instead, so that the concave surface of the solution is exactly tangent to the volume scale line of the solution we need to prepare.

7. Shake well: cover the cork, use the index finger to hold the cork, the fingers of the other hand hold the bottom of the bottle, repeatedly upside down and down, so that the solution is mixed evenly, and then label the solution bottle, mark the solution name, concentration, preparation date, preparation personnel, shelf life and other information.

The preparation of a solution refers to the dissolution of a certain amount of solute in a solvent to bring it to the desired concentration. The following are the general solution preparation steps:

1.Determine the concentration and volume of the solution to be prepared.

2.Prepare the required solutes and solvents. The solvent should be pure and free of impurities.

3.Weigh the solute, add it to an appropriate amount of solvent, and stir well until it is completely dissolved.

4.If you need to adjust the concentration of the solution, you can add an appropriate amount of solvent or solute, and stir it well again after the ants are sleepy.

5.Finally, use an accurate container such as a volumetric flask to set the volume of the solution to the desired volume and shake it well.

In the process of preparing the solution, the following points need to be noted:

1.Soluts and solvents should be prepared in a certain proportion to avoid excessive or insufficient amounts.

2.The stirring time should be sufficient to ensure uniform dissolution.

3.When setting the volume, pay attention to the marking line of the container to avoid errors.

4.Attention should be paid to laboratory safety during the preparation process to avoid mishandling of chemicals.

The above are the general solution preparation steps and precautions, I hope it can be helpful to you.

The preparation of standard solutions mainly includes the following points:1) Direct method.

A certain amount of dried reference material is accurately weighed on an analytical balance, dissolved and quantitatively transferred to a calibrated volumetric flask, diluted to scale with distilled water, and shaken well.

2) Calibration method.

Calibration: The process of determining the concentration of a standard solution using a reference substance or a solution of known exact concentration.

Direct calibration (calibration with reference material): accurately weigh a certain amount of reference material, dissolve it in water and titrate it with the standard solution to be measured, until the medical education network collects and sorts out the reaction.

Indirect calibration: The standard solution to be tested is calibrated with another standard solution of known concentration.

A few notes:The standard solution is prepared and calibrated by a special person.

Standard solutions should be calibrated at regular intervals.

Each vial of reagent solution must be labeled with the name, specification, concentration, and configuration.

There are two standards for the preparation and calibration of standard solutions, namely SH T0079 "Preparation Method of Reagent Solution for Petroleum Product Testing" and GB T601-2002 "Preparation of Standard Titration Solution for Chemical Reagents".

The preparation of the solution is as follows:

1. Calculation: Calculate the mass of the solid solute or the volume of the liquid concentrated solution required for the preparation of the banquet hall.

2. Weighing: Weigh the solid mass with a tray balance or use a measuring cylinder (a pipette is used, but a measuring cylinder is generally used in middle school) to measure the volume of liquid.

3. Rushi dissolve: dissolve or dilute the solute in a beaker and return to room temperature (if it cannot be completely dissolved, it can be heated appropriately). Check the volumetric flask for water leaks.

Solution preparation: bench scale (or balance), medicine spoon, beaker, glass rod, graduated cylinder (or measuring cup), volumetric flask (fine-mouthed bottle), pipette, rubber tip dropper, surface dish.

Precautions: Sodium hydroxide is an alkaline chemical, concentrated hydrochloric acid is an acidic chemical, be careful not to splash on your hands and body, so as not to corrode!

Pay attention to the accuracy of the calculations; Pay attention to the use of pipettes; To dilute concentrated sulphuric acid, acid is added to water and stirred with a glass rod.

Volumetric flasks must be tested for leaks before use, and the steps for leak detection are to fill tap water near the marking line and close the cork. Hold the bottom of the bottle with your right hand, stand upside down for 2min, and observe whether the cork is seeping. If there is no leakage, rotate the plug 180 degrees and then detect the leak.

If there is water leakage, you need to change a set of volumetric flasks and then test for leakage.

When configuring the solution diluted from concentrated liquid, such as dilute sulfuric acid from concentrated sulfuric acid, the graduated cylinder used to weigh concentrated sulfuric acid should not be washed, because the graduated cylinder has been designed with the phenomenon of residual liquid in mind, so as not to cause changes in the amount of solution substances!

Before pipetting, it should be allowed to stand until the temperature of the solution returns to room temperature (such as sodium hydroxide solid dissolved in water to release heat, concentrated sulfuric acid dilute to release heat, ammonium nitrate solid dissolved in water to absorb heat), so as not to cause thermal expansion and contraction of the volumetric flask!

The preparation solution is described as follows:

In chemistry, the process of preparing a solution with chemicals and solvents (usually water) to the concentration required for the experiment is called preparing a solution. Before preparing the solution, you need to calculate the amount of items needed and clean the instrument.

Calculations: n=m m, c=n v, m v. Examples:

The laboratory prepared a hydrochloric acid solution with a density of concentrated hydrochloric acid with a mass fraction of 250ml. v=m/p=(。Weigh or measure:

Solid reagents are weighed on an analytical balance or electronic balance (to match the accuracy of volumetric flasks), and liquid reagents are weighed in graduated cylinders. Dissolve: Put the weighed solid into a beaker and dissolve it with an appropriate amount (20 30 ml) of distilled water.

Rewarming: Wait for the solution to cool and move into a volumetric flask. Transfer (pipetting):

Due to the thin neck of the volumetric flask, in order to avoid the liquid from spilling outside, drain with a glass rod, the glass rod can not be close to the mouth of the volumetric flask, and the bottom of the rod should be leaned against the scale line of the wall of the volumetric flask. Washing: Wash the inner wall of the beaker 2 3 times with a small amount of distilled water, and transfer all the washing liquid to the volumetric flask.

Primary mixing: Gently shake the volumetric flask to mix the solution evenly.

Constant volume: Add distilled water to the volumetric flask, and when the liquid level is 1 2cm below the scale line of the capacity bottleneck, use a rubber head dropper to add distilled water dropwise until the liquid level is tangent to the scale mark. Shake well, cover the cork and turn it upside down repeatedly, shake well, if the liquid level drops, do not add water to set the volume.

Since the flask cannot hold the solution for a long time, the prepared solution is transferred to the reagent bottle and labeled.

Rubber tip dropper:

The rubber head dropper, also known as the rubber cap dropper, is an instrument used to suck or add a small amount of liquid reagent dropwise. The rubber tip dropper consists of a rubber cap and a glass tube. There are several forms, such as straight, straight with buffer balls and curved with buffer balls.

The specifications of the rubber head dropper are expressed in terms of tube length, and there are two types of pipes: 90 mm and 100 mm. Glue tip dropper per drop.

Take the preparation of 500ml of sodium hydroxide solution as an example to introduce the operation steps.

1. Calculation: Using the formula n=m m, c=n v, the amount of sodium hydroxide m is calculated, that is, m=cvm=

2. Weighing: weigh 2 grams of sodium hydroxide with a balance and put it in a beaker;

According to the volume of the solution prepared by Zheng Kuo, select a 500ml volumetric flask, the mass of sodium hydroxide = 500ml 10-3l ml, 3, dissolve:

Pour a certain amount of distilled water into a beaker containing sodium hydroxide and stir it with a glass rod to dissolve;

4. Pipetting: Inject the cooled sodium hydroxide solution into a 500ml volumetric flask along the glass rod;

5. Washing: Wash the cup with distilled water 2 3 times, and inject the washing liquid into the volumetric flask;

7. Constant volume: carefully add distilled water to the volumetric flask until the liquid level is close to the scale 1 2, and use the rubber head dropper to add dropwise, and the liquid level of the solution is just tangent to the scale mark;

8. Shake well: the concentration of the solution after the volume is uneven, the stopper of the volumetric flask should be corked tightly, the stopper should be pressed against the stopper with the index finger, the bottom of the bottle should be supported by the fingers of the other hand, and the volumetric flask should be reversed and shaken many times to make the solution mixed evenly;

9. Bottling and labeling:

Pour the prepared sodium hydroxide solution into the reagent bottle, close the cork and label it.