How to titrate the total acid, total base, free acid, and free base of the solution

Determination of free acids.

Absorb 10ml of the solution to be tested in a 250ml Erlenmeyer flask, add 50ml of distilled water, add 3 drops of bromophenol blue indicator, and titrate with the prepared sodium hydroxide solution to light blue as the end point.

Free acidity (point) is calculated according to Eq. (3):

vc Free acidity (point) 3).

Where: v - volume of sodium hydroxide standard titration solution, ml;

c - concentration of sodium hydroxide standard titration solution, n

When the concentration of the prepared sodium hydroxide solution is 10ml, then equation (3) can be written:

Free acidity (point) v(4)

Determination of free alkalinity.

Absorb 10ml of the solution to be tested in a 250ml Erlenmeyer flask, add 50ml of distilled water, add 3 drops of phenolphthalein indicator, and titrate with the prepared hydrochloric acid solution to colorless as the end point.

The free alkalinity (point) is calculated according to equation (1):

vc free alkalinity (point) 10 vc(1)

Where: v - volume of hydrochloric acid standard titration solution, ml;

c - concentration of hydrochloric acid standard titration solution, n

When the concentration of the prepared hydrochloric acid solution is 10ml, then equation (1) can be written:

Free alkalinity (point) v(2)

Determination of total acidity.

Absorb 10ml of the solution to be tested in a 250ml Erlenmeyer flask, add 50ml of distilled water, add 1 2 drops of phenolphthalein indicator, and drop it with the prepared sodium hydroxide solution until pink as the end point.

Total acidity (point) is calculated according to Eq. (5):

v×c 10

Total acidity (point) 50 V C(5)

Where: v - volume of sodium hydroxide standard titration solution, ml;

c - concentration of sodium hydroxide standard titration solution, n

When the concentration of the prepared sodium hydroxide solution is 10ml, then equation (5) can be written as:

Total acidity (point) v(6)

Summary. Free Alkali Test Method 1Method:

Weigh 1g of the sample (weighed to the calculation of dry basis) in a 50ml beaker, add 30ml of 60% ethanol solution, semi-immerse in a constant temperature water bath (water bath temperature 52 1) heating stirring leaching, wait for the liquid temperature to rise to 45, continue to stir and leach at 45 50 for 3 minutes. Use 250 300 mesh, nylon sieve silk to filter the leaching solution into a 250ml triangular beaker, add 30ml of 60% ethanol solution to the remaining sample in the cup and continue to heat and stir leach for 1 minute in the same method, filter with the same method, and finally wash the sample with 15ml of 60% ethanol solution and filter it in the same triangular flask, accurately add the standard sulfuric acid solution, then add 50ml of distilled water and put it on the electric stove to heat and boil for 2 minutes to cool, add 2 3 drops of methyl red indicator, and drop the sodium hydroxide standard solution to the end point to show yellow.

Free Alkali Test Method 1Methods: Weigh 1g of the sample (weighed to the calculation of dry basis) and put it in a 50ml beaker, add 30ml of 60% ethanol solution, semi-immerse it in a constant temperature water bath (water bath temperature 52 1) to heat and stir for leaching, wait for the liquid temperature to rise to 45, and continue to stir and leach at 45 50 for 3 minutes.

Use 250 300 mesh, nylon sieve silk to filter the leaching solution into a 250ml triangular beaker, add 30ml of 60% ethanol solution to the remaining sample in the cup and continue to add Zheng with hot stirring to leach for 1 minute, filter with the same method, and finally wash the sample with 15ml of 60% ethanol solution and filter it in the same triangular flask, accurately add the standard sulfuric acid solution, then add 50ml of distilled water and put it on the electric stove to heat and boil for 2 minutes to cool, add 2 3 drops of methyl red indicator, The sodium hydroxide standard droplet is just yellow at the end point.

I would like to know how to determine if the extraction is a complete, easy way.

Free alkalinity generally refers to the content of free (that is, independent and complete alkali state or structure exists) in the system. 2. The total alkalinity is detected, and then converted.

Acid-base titration, generally according to the structure and properties of the compound, first all the alkali is made, the total alkali amount is calculated by titration, then derivative, then titrated, and then subtracted to obtain the content of free alkali annihilation.

For example, in the experiment of determining the content of procaine hydrochloride, chloroform is extracted several times, which is to extract the organic alkali inside, how to determine that the extraction is complete?

Find a substance that reacts with it and there is a noticeable change, and add it. If there is a reaction, there is still a response, and if there is no response, there is none.

Right! I want to know what to add ...

I don't know <> either

It depends on his basic attributes.

Ahh Awesome! 

Sorry, but I don't have a lot of expertise in this area.

It's okay, brother, fate, goodbye! 

Haha, goodbye.

Yes, the principle of acid-base titration is to use the analysis method of proton transfer reaction based on acid and base in water, therefore, as long as it is acid and base, the titration reaction can be carried out, strong acid + strong base: H+ + OH- = H2O

But not every strong acid reacts with a strong base is like this, for example, barium hydroxide reacts with sulfuric acid Ba2+ +2OH- +SO4 2- +2H+=BaSO4 (precipitation) +2H2O

Strong acid and weak alkali hydrochloric acid + copper hydroxide: 2H+ + Cu(OH)2=Cu2+ +2H2O

Weak acid and strong base Acetic acid and sodium hydroxide OH- +CH3COOH==CH3COO- +H2O

Weak acid and weak base Acetic acid and copper hydroxide 2ch3cooh+cu(OH)2=2ch3coo- +2H2O+Cu2+

When writing the ion equation, it is necessary to pay attention to whether the redox reaction can occur between the reactants, and at that time, the calcium hydroxide chemical formula should be disassembled when the clarified lime water reacts, and it cannot be disassembled when the reactants are lime milk.

1. After rinsing with the solution to be measured, there will be a small amount of liquid residue on the bottle wall, assuming that m, for example, the amount of solution to be titrated is A, and the actual titration, the amount of NaOH that reacts with the acid is A+M, and the amount brought in when calculating the concentration is A, M is not counted, and the calculation result will be large.

2 Distilled water does not affect because distilled water does not participate in the reaction, the total amount of NaOH does not change, and the amount of acid consumed by titration does not change, or the titration has nothing to do with NaOH concentration.

3. There are bubbles in the nozzle before titration, and the bubbles are filled with acid after titration, assuming that acid M is used for filling, and acid B is used for titration in total, the acid used in the actual neutralization reaction is B-M, and when calculating is B, the acid consumed by the calculation result will be greater than the actual amount consumed, so the calculation result is high.

4 From the beginning of the titration to the end of the calculation, the NaOH concentration was not used, and there was no effect on the concentration of higher or smaller concentrations.

Why is the concentration of NAOH high when you wash the Erlenmeyer flask with the solution to be measured,-- because you wash the Erlenmeyer flask with the solution to be tested, there will be a small amount of sodium hydroxide left in the Erlenmeyer flask, and you add 20 ml of sodium hydroxide when you measure it, which may be 21 ml in it. The more hydrochloric acid is needed, the higher the concentration.

After the Erlenmeyer flask is washed, there is still a small amount of distilled water in the bottle, which has no effect on the NaOH concentration--- and a small amount of distilled water in the Erlenmeyer flask, which has no effect on the total amount of sodium hydroxide.

Why is there air bubbles in the tip of the burette before titration, the NAOH concentration is high--- there are bubbles in the tip of the burette, you actually add the bubbles as hydrochloric acid drops. Actually, 10 ml of hydrochloric acid was used, but because of the bubbles, you think it was 11 ml, so the concentration of sodium hydroxide is on the high side.

Why does the addition of a small amount of distilled water in the Erlenmeyer flask have no effect on the NaOH concentration during the titration--- the addition of distilled water has no effect on the total amount of sodium hydroxide, so it has no effect on the concentration.

1. After washing the Erlenmeyer flask, it is washed with the solution to be tested, and then the liquid is taken, and the actual amount of the liquid to be tested increases and the measurement result is that the concentration is high. 2. The liquid to be measured cannot be taken with a graduated cylinder, because the graduated cylinder is a rough measuring tool, and the index value is 1 50 of the maximum amount, and the accuracy is low, but the liquid can be taken with a pipette. 3. After the burette is washed, the standard solution is directly loaded without rinsing with the standard solution, which causes the standard solution to be diluted, and the volume consumed in the titration increases, and the measurement result is that the concentration of the solution to be measured is high.

4. There are bubbles in the tip of the burette before titration, and the bubbles disappear after titration, and the bubbles are calculated as standard liquid volume, resulting in a high concentration of the measurement results. 5. During the titration process, the standard liquid drops to the outside of the Erlenmeyer flask, or the burette containing the standard liquid leaks, and when reading, the V mark is large, resulting in the measurement result that the concentration of the liquid to be measured is large. 6. After washing the burette of the liquid to be tested, the liquid is taken into the Erlenmeyer flask without being moistened with the solution to be measured, resulting in the dilution of the solution to be tested and the concentration of the measurement result is low.

7. The reading is not accurate, for example, the burette containing the standard solution, looking up before the titration, the reading is too large, and looking down after the titration, the reading is too small. As a result, the difference in the volume of the calculated standard liquid is small, and the concentration of the liquid to be measured is low. 8. The liquid to be tested splashes outside the Erlenmeyer flask or is attached to the upper part of the bottle wall and is not neutralized by the standard solution, and the concentration of the solution to be tested is low.

9. The standard solution is not shaken well after dropping into the Erlenmeyer flask, and the titration is stopped without waiting for half a minute to observe whether the discoloration is stable, resulting in the titration not reaching the end point, and the concentration of the solution to be measured is low.

This question is very simple, you just need to pay attention to the relationship between titration and the titration reaction satisfaction, and then look at which moles of change are caused by those wrong operations, and it will be very simple to practice a few more, you should study hard in high school, and if you study chemistry in college, you will realize that the knowledge in high school is really good, oh yes, remember to keep your notes.

Determination of free acid-base in calcium propionate?

The free acid is calculated as CH3CH2COO, the free base is calculated as NAOH, and the acid-base reaction is calculated.

Because the amount of titration is small, it is necessary to add the burette drop by drop, and it is best to add it with a pipette because propionic acid is a strong acid, calcium hydroxide is a strong base, and if there is a reaction, it will not contain both free acid and free base.

Free acid or base is calculated according to the acid-base reaction, there is no possibility of both free acid and free base samples, it must be titrated with a burette, skilled operation is the premise of accurate titration, only skilled laboratory technicians can accurately titrate to the end point, without excessive dropping.

Acid rate = free acid of the total acid, plus the size of the original opioid phosphate adjustable content ratio.

When the titration endpoint is reached, the pH of the mixed solution is already less than or equal to, not the pH = 7 obtained by the complete reaction of acid and baseHowever, the error is within the range of the error of the titration analysis, so it is feasible.

The abrupt range of sodium hydroxide at the concentration of mol L is qualified when the concentration is mol L.

Sulfuric acid is a dibasic acid and consumes two parts of sodium hydroxide solution. I don't know if you didn't think of it here, the answer should have an M.

I'll explain it to you:

1. Your first question did not give the full condition, and I don't know the amount of hydrochloric acid solution used when using phenolphthalein as an indicator. But I can tell you how to solve the problem. These two questions examine the problem of mixed base titration.

You have to understand that when phenolphthalein is used as an indicator, it can only turn sodium carbonate into sodium bicarbonate, but not carbonic acid. That's it.

The titration of mixed bases generally uses phenolphthalein as an indicator, titrates to the endpoint, and then adds methyl orange titration, a total of two titration endpoints. Assuming that the volume of HCl consumed in the first segment is V1 and the volume of HCl consumed in the second segment is V2, the mixture of the two bases can be determined based on the size of V1 and V2. When NaOH and Na2CO3 are contained, V1 > V2, because the first titration neutralizes all NaOH and titrates Na2CO3 to NaHCO3, and the second titration converts all NaHCO3 into NaCl, so the HCl volume consumed by Na2CO3 is 2 times that of V2, and the volume consumed by NaOH is (V1-V2); When NaHCO3 and Na2CO3 are contained, V1 adds to the follow-up question: In fact, it is very simple, take the first question as an example, V1=40 ml, assuming that the content of NaOH is X, then the content of NaCO3 is 1-X. According to the first and second segments, the two equations are titrated respectively, and the x can be solved.

There are specific calculation formulas in the book. The variation of this problem is simply to solve the system of equations.