1. After the acid burette is washed with distilled water, it is directly loaded into the standard solution, which leads to dilution of the standard solution, reduction of the solution concentration, large consumption of the standard solution during titration and high determination results.
2. After the alkaline burette is washed with water, the solution is added into the conical flask, which is not wetted by the solution to be tested, and the solution to be tested is diluted, so the determination result is low (the concentration of the determined solution is lower than the actual solution).
3. After the conical bottle was washed with water, it was wetted with the liquid to be tested, and then the liquid to be tested was taken, which led to an increase in the actual consumption of the liquid to be tested and a high determination result (the volume of the liquid used was higher than the actual volume).
4. When the liquid to be tested is taken out from the basic burette, the liquid is sucked into the conical bottle when the bubbles are not discharged from the tip of the burette. Because the actual volume of the liquid to be measured is reduced, the determination result is low.
5. Before titration, rinse the conical flask with water, or dry the residual water in the conical flask, or after taking the liquid to be measured, add some water to the conical flask for easy observation. Although the volume of the measured liquid has increased, the measured volume remains unchanged, so it has no effect on the final result.
6. Before titration, the liquid level of the acid burette was above the "0" scale line, and the liquid level was not adjusted, resulting in a smaller standard liquid volume and a lower measurement result (the measured volume is lower than the actual volume).
7. The alkaline burette puts the liquid to be measured into the conical bottle, so that the liquid to be measured splashes out of the conical bottle or adheres to the upper part of the bottle wall without being neutralized by the standard liquid, resulting in a small volume of the standard liquid during titration and a low determination result (the volume of the liquid to be measured is lower than the actual volume).
8, acid burette, looked up before titration reading, head-up reading after titration, resulting in a decrease in the volume of standard solution, the determination result is low (the measured volume is lower than the actual volume).
9. For acid burette, check the burette scale line before titration, and check the scale line after titration. The reading is too large, resulting in a large standard liquid volume and a high measurement result (the measured volume is higher than the actual volume).
10. Before titration, there are bubbles at the tip of the acid burette. After titration, bubbles disappear, and the volume occupied by bubbles is filled with some standard solutions, which leads to the increase of standard solution volume and higher measurement result (the measured volume is lower than the actual volume).
1 1. During titration, standard hydrochloric acid dripped from the conical flask, resulting in a large standard liquid volume and a high determination result (the measured volume is lower than the actual volume).
12. After the end of titration, a drop of standard solution is suspended at the tip of burette, resulting in a decrease of standard solution actually entering the conical flask, which leads to a larger standard solution volume and a higher measurement result (the measured volume is higher than the actual volume).
13, the color change of the solution does not last for 30 seconds, that is, titration is stopped, and as a result, the original color of the solution is restored, resulting in a decrease in the volume of the standard solution and a low determination result.
Extended data:
Matters needing attention in acid-base neutralization titration:
First, when shaking the bottle, the wrist should move slightly to make the solution circulate in one direction, but don't make the bottle mouth contact the burette, and the solution can't overflow.
Two, titration, the left hand can't leave the cock to let the liquid flow down.
Third, pay attention to the color change of the solution around the dropping point. At the beginning, it should be dropped while shaking, and the titration speed can be slightly faster (3~4 drops per second is appropriate), but it should not form a continuous water flow. When approaching the end point, add a drop instead, shake it several times, and finally add half a drop, that is, shake the conical flask until the color of the solution changes obviously and does not fade within half a minute, so as to reach the end point accurately.
Do not look at the volume above the burette when titrating, regardless of the progress of the titration reaction. The method of adding half a drop of solution is as follows: gently rotate the piston to make the solution hang on the outlet to form half a drop (sometimes less than half a drop), and scrape it off with the inner wall of the conical bottle.
Fourthly, it is best to start each titration from "0.00" ml (or from a certain section near 0ML), so that a certain section of the burette can be fixed to reduce the volume error.
Five, calculation should be paid attention to (acid titration)
The conical flask does not need to be wetted and cleaned.
B the acid burette was not wetted with standard solution, and the result was on the high side.
Six, data processing
In order to reduce the experimental error, it is required to repeat the experiment for 2~3 times, find out the average volume of the standard solution used, and then calculate the quantitative concentration of the substance in the liquid to be measured.
References:
Baidu encyclopedia-acid-base neutralization titration