How to increase the concentration of NaOH solution with chemical methods without adding impurities.

Sodium peroxide or sodium oxide is put into sodium hydroxide, sodium peroxide meets water to generate sodium hydroxide and oxygen, oxygen is extremely insoluble and water is released, and sodium hydroxide solution can be formed without impurities, but note that generally do not say "pure" sodium hydroxide solution. The same is true for sodium oxide, but it does not produce oxygen.

Because the solution is composed of two parts, namely solute and solvent, if you want to solve the problem of changing the concentration of the solution, you can consider both solute and solvent

1) Increase solute i.e. increase pure NaOH crystals. However, pay attention to the saturation of the solution

2) Reduce the solvent The mass of the solvent is reduced, and the mass of the solute remains unchanged, which can also increase the concentration of the solution Because NaOH is an ionic crystal, the method of heating with an alcohol lamp can be used, and the mass of the solvent is reduced

When the water is ionized by electricity, the water is reduced, and the concentration is naturally higher. When the NaOH solution reaches saturation, the concentration does not change.

Sodium oxide or sodium peroxide can be reacted with water to form sodium hydroxide, which is a chemical reaction and meets your requirements!

In fact, it doesn't matter, as long as the amount of NAOH can be increased by chemical methods, such as adding Na2O, Na, Na2O2, etc.

Heating with an alcohol lamp will do, and NaOH is an ionic crystal.

Add NA or NA2O or NA2O2 or NAH

Or electrify the solution, electrolyze water: 2H2O 2H2+O2

Density = mass divided by volume.

Because of sodium hydroxide.

It is very easy to absorb water vapor and carbon dioxide in the air.

It is not possible to accurately weigh its mass, so it can only be used indirectly to prepare a solution with a similar concentration, and then calibrate it with potassium hydrogen phthalate solution, which is similar to concentrated hydrochloric acid.

Some are similar. Preparation and calibration of sodium oxide.

1. Preparation Weigh 100g of sodium hydroxide, dissolve it in 100ml of water, shake well, and inject polyethylene.

In a container, place tightly closed until the solution is clear. Siphon with a plastic tube.

5 ml of the supernatant, inject 1000 ml of carbon dioxide-free water and shake well.

2. Calibrate the potassium hydrogen phthalate weighed in 105 110 baked to constant weight of the benchmark, accurate to, dissolved in 50ml of carbon dioxide-free water, add 2 drops of phenolphthalein indicator (10g L), titrate with the prepared sodium hydroxide solution until the solution is pink, and make a blank test at the same time.

3. Calculate the concentration of sodium hydroxide standard solution according to the following formula.

c(naoh)=m/(v1-v2)*

where C(NaOH) is the concentration of the substance of the amount of sodium hydroxide standard solution, mol l;

v1 - dosage of potassium hydrogen phthalate for titration, ml;

V0 - the amount of sodium hydroxide solution in the blank test, ml;

m - the mass of potassium phthalate, g;

The amount of potassium phthalodia expressed in grams equivalent to sodium hydroxide standard solution [c(NaOH)=.

Since NaOH is prone to deliquescent, there is no way to weigh it accurately (analytical balance), so it is calibrated with potassium hydrogen phthalate (KHP)!! The molecular weight of potassium hydrogen phthalate is, this must be precise. Phenolphthalein acts as an indicator and can titrate the amount of NaOH you have roughly configured for the concentration of the substance.

The hidden principle here is that NaOH is prone to deliquescent, while KHP (yellow crystal) is non-deliquescent and stable.

NaOH is highly absorbent and absorbs CO2 from the air, so your NaOH standard solution often contains Na2CO3. The way to overcome it is to prepare NaOH into a saturated solution, because Na2CO3 is almost insoluble in the saturated NaOH solution and will slowly precipitate out, and at this time the supernatant is very pure NaOH and then diluted to the required concentration. Distilled water for preparation should be heated and boiled first, CO2 should be removed, and then cooled before use.

Summary. The solute of NaOH decreases, but the total solute mass increases because of the partial absorption of CO2 from the air

If the NaOH solution is prepared, the weighing time is too long, which leads to the increase of the mass of the solute in the solution, and the result is too high.

Dear, what is the specific question?

If the NaOH solution is prepared, the weighing time is too long, which leads to the increase of the mass of the solute in the solution, and the result is too high. Right.

The solute of the right NaOH will decrease, but the total solute mass will increase because the CO2 in the air is partially absorbed

Sodium carbonate is generated.

Neither HCL nor NaOH standard solution can be prepared by direct method, because HCl is highly volatile, and the base model will volatilize in the process of direct configuration, while NaOH will absorb CO2 in the air, and no matter how fast the configuration process is, some sodium hydroxide will slowly undergo chemical reactions and cause deterioration.

Experiment: 1Identify the two bottles of solution.

2.Pour some sodium hydroxide into a beaker and add a few drops of phenolphthalein dropwise, and find that it turns red.

3.Hydrochloric acid was added, and it was found that the red color faded and the temperature of the solution increased.

4.Fading red indicates that the alkalinity is gone, so the sodium hydroxide reacts off.

5. naoh+hcl→nacl+h2o。

The reason why both HCl and NaOH standard solutions cannot be prepared by the direct method is that they are unstable in air and do not meet the quantitative conditions for direct preparation of standard solutions.

Specifically, HCl is highly volatile, so its standard solution can only be prepared using the calibration method.

NaOH is a very liquid that absorbs moisture in the air and deliquescent, so its standard solution can only be prepared by calibration.

The specific calibration method is HCl standard solution, which is calibrated with sodium carbonate, the reference substance. NaOH standard solution, calibrated with the reference substance potassium hydrogen phthalate.

Answer] D Answer Analysis] Test Question Analysis: According to C=N V, the factors that affect the amount and concentration of substances are the amount of dissolved substances and the volume change of the solution.

A The NaOH used has absorbed moisture, resulting in a decrease in the amount of solute substances, and the concentration of the prepared solution is low, A does not meet the topic;

b A small amount of distilled water remains in the volumetric flask at the beginning, which has no effect on the concentration of the solution, and b does not conform to the topic;

c A small amount of NaOH solution remains in the beaker, resulting in a decrease in the amount of solute substances, and the concentration of the prepared solution is low, C does not meet the topic;

d When adding water to the volumetric flask, the eyes have been looking down at the liquid level, resulting in a decrease in the volume of solvent, and the concentration of the beam solution is high, D is in line with the topic, so D is selected.

Test point: the amount and concentration of the substance.

Comments: This question examines the quantity and concentration of substances, and the answer to such questions should pay attention to the factors that affect the quantity and concentration of substances, and the analysis of various experimental operations, and the difficulty of the questions is medium.

【Answer】C [Answer Analysis] Test Question Analysis: Sodium peroxide is dissolved in water to produce sodium hydroxide and oxygen, and the equation of the reaction is H2O 2Na2O2 = 4NaOH O2. That is, the mass of the solvent decreases after the reaction, while the mass of sodium hydroxide increases.

And because the solution is a saturated solution before the reaction, there must be solid precipitation after the reaction, but the solution is still a saturated solution after precipitation, and the temperature of the solution is unchanged, so the concentration of the solution is unchanged, and the answer is c.

Test center: Examine the judgment and application of the properties and solubility of sodium peroxide.

Comments: This question belongs to the common college entrance examination question type, which is a moderately difficult test question. The key to this question is to correctly grasp the meaning of the solubility of the substance, and then the correct examination of the question is also the key to the solution.

This question is conducive to cultivating students' thinking rigor and problem-solving ability.

1 to 7 will affect, explained below:

1, will; When weighing solid solutes, the left deviation of the tray balance pointer increases the solute, and the concentration of the prepared solution will become larger.

2, will; Sodium hydroxide can react with carbon dioxide in the air and deteriorate 2NaOH + CO ==Na CO + H O The concentration of the prepared solution will be smaller.

3. Yes; Leaving some distilled water in the volumetric flask before dispensing is equivalent to increasing the solvent, and the concentration of the prepared solution will become smaller.

4. Yes; Forgetting to wash the beaker when transferring the preparation will leave a part of the solution in the beaker and the concentration of the prepared solution will be reduced.

5, will; When the volume is fixed, the dropper and distilled water exceed the scale mark, which is equivalent to increasing the solvent, and the concentration of the prepared solution will become smaller.

6, will; When the eyes look down at the liquid level at the end of the volume, the solution will be small, and the concentration of the prepared solution will become larger.

7, will; After shaking well, it is found that the liquid level is lower than the degree line, and water is added, which is equivalent to increasing the solvent, and the concentration of the prepared solution will become smaller.

No, you can rest assured and answer decisively.