What is the effect of acidity calibration on the calibration of Na2S2O3 solutions with the KIO3 refe

Because the titration endpoint is not easy to see, it is easy to overdose, which leads to error.

K2Cr2O7 is stable and does not need to be calibrated, and the solution can be directly used for titration.

KMno4 (when stored) is unstable, and the solution needs to be calibrated and then titrated with KMNO4.

So in fact, both kinds can titrate Na2S2O3, but K2Cr2O7 is generally chosen.

This titration method is the indirect iodometry. K2Cr2O7 can be reduced by Ki by differential osmosis, quantitatively replaced with iodine, and then titrated with Na2S2O3 standard or Qingsheng quasi-solution to produce I2. I studied analytical chemistry, and I have been thinking about this question for a long time, and the answer I gave is no.

Because SiO2 is very stable, it is insoluble in water and does not react with water, and does not interact with ordinary acids. The conditions of this titration are neutral or weakly acidic, and SiO2 will not participate in the reaction. So it doesn't affect.

This is a matter of color and should be titrated with acidic potassium permanganate.

The titration endpoint is not easy to see and is prone to overdose, which leads to errors.

Dilution serves two purposes:

1) Potassium iodide.

Part of sulfuric acid and potassium iodate will be added to the configuration.

The reaction needs to be reacted under acidic conditions. and iodine and sodium thiosulfate.

The reaction needs to be neutral or slightly acidic, so dilution before titration can reduce the acidity of the reaction solution and facilitate the reaction.

2) The color of iodine element is very dark, and the reaction with starch indicator is very sensitive, and the dilution can avoid the misjudgment of the titration endpoint due to too dark color.

Precautions in calibration experiments.

When calibrating HCl standard solutions using the reference material Na2CO3, the purpose of heating and boiling the solution near the end point is to ensure a complete reaction and eliminate the dissolution of carbon dioxide. During this process, if the solution changes color, it may indicate that Na2CO3 has completely reacted and the endpoint has been reached. At this point, the volume reading at the end point can be recorded to calculate the concentration of the HCl standard solution.

The reaction between Na2CO3 and HCl is a neutralization reaction that can be expressed by the following argument:

na2co3 + 2hcl → 2nacl + h2o + co2

Sodium carbonate + hydrochloric acid Sodium chloride + water + carbon dioxide.

Initially, the carbonate ions in the Na2CO3 standard solution and the hydrogen ions in the HCl standard solution react rapidly to form NaCl and water, while carbon dioxide gas is produced. Until the endpoint is reached, unreacted bases and acids remain in the solution. When the end point is approached, heating the boiling solution helps to speed up the reaction rate, allowing the remaining bases and acids to react quickly, ensuring the adequacy of the reaction.

If the color changes, it may mean that the end point has been reached. When calibrating the HCl standard solution, the solution showed alkaline blue or lack of green at the beginning, and with the dropwise addition of HCl, the solution was gradually neutralized and the color gradually changed. At the end point, the solution changes from alkaline blue or green to neutral colorless.

This color change can be used as an indicator to determine the end point.

It should be noted that care should be taken when adding acid to the titration to avoid over-adding acid drops that may lead to reversal of the reaction beyond the endpoint. At the same time, the boiling process is controlled to avoid splashing and stuffing and spilling of the solution.

1) Use the reference substance Na2CO3 to standardize the HCl standard and slow the solution A file base orange terminus orange to turn red!

2) Heat the boiling solution to expel CO2 and prevent the end point from being advanced!

In the process of calibrating HCl standard solutions, if the reference Na2CO3 contains a small amount of NaHCO3, it will affect the calibration results. Because the molar mass of NaHCO3 and Na2CO3 is different, the presence of NaHCO3 needs to be taken into account when calculating the molar concentration of Na2CO3.

One solution is to mix the Na2CO3 solution side by side with the phenolphthalein indicator prior to calibration, and then add a small amount of HCl standard solution to record the endpoint of the color change. Next, a small amount of NaHCO3 solution was added, followed by an HCl standard solution, and the endpoint of the color change was recorded. By comparing the endpoints of the two volumes, the molar concentration of Na2CO3 can be calculated.

Another solution is to remove NaHCO3 from the Na2CO3 solution prior to calibration. The method of acid treatment can be used, the Na2CO3 solution is added with an appropriate amount of acid to convert NaHCO3 to CO2 and H2O, and then the acid is neutralized with alkali so that the solution no longer contains acid and CO2. After removing NaHCO3, it can be calibrated.

The reference substance used for the standard nuclear sedan hand to modify the Na2S2O3 solution is ().

Correct Answer: B

Summary. When using KBRO3 to calibrate Na2S2O3, excessive KI and H2SO4 solutions were added to ensure the completeness and accuracy of the reaction. First of all, the addition of excess Ki can cause KBRO3 to react with I- to form I2, which can increase the reaction rate and reaction completeness.

At the same time, I2 can react with Na2S2O3 to form Na2S4O6, so the consumption of I2 can be detected with a starch indicator, thus determining the stoichiometric ratio between KBRO3 and Na2S2O3.

When using KBRO3+ as a reference material to calibrate Na2S2O3, why do we add an excessive amount of Ki and H2SO4 solution, and why?

When using KBRO 3 to calibrate Na2S2O3, an excess of Socks Ki and H2SO4 solutions were added to ensure the completeness and accuracy of the reaction. First of all, the addition of excess Ki can cause KBRO3 to react with I- to form I2, which can increase the reaction rate and reaction completeness. At the same time, I2 can react with Na2S2O3 to form Na2S4O6, so the stoichiometric ratio between KBRO3 and Na2S2O3 can be determined by detecting the consumption of I2 with a starch indicator.

Why should it be diluted with water before titration?

When performing titration experiments, it is usually necessary to dilute the solution of the substance to be measured to a certain concentration range in order to facilitate the operation of the post-vertical balance and accurately measure the required volume. This dilution can be achieved by adding the right amount of water.

Secondly, the addition or excessive addition of H2SO4 solution can ensure that the pH of the reaction system is appropriate, and it is conducive to promoting the reaction. In addition, H2SO4 can also decompose KBRO3 into Br2 and O2, which can better ensure the completeness and accuracy of the reaction.

The Na2S2O3 standard titration solution was coarsely buried and directly calibrated with K2Cr2O7. () Shiye Town.

a.That's right. b.Mistake.

Correct answer: B