What are the irregularities when using burettes for titration?

The burette must be tested for leakage before use. The method is: burette live plug is not greased, water is injected to full capacity, and it is allowed to stand vertically for 15min, and the leaked water does not exceed the minimum index value, and it can be used.

2) When injecting the standard solution into the burette, the burette should be rinsed 2 or 3 times with a small amount of standard solution. Inject the standard solution to a few centimeters above the "0" scale, in the case of an acid burette, turn the plug to quickly fill the nozzle of the solution, and there should be no bubbles; In the case of an alkaline burette, bend the latex tube upwards and squeeze the glass bulb inside the tube to fill the hose and glass tip with the solution. Adjust the burette contents so that it is on the "0" scale.

3) The burette must be kept vertical when reading. After the solution is loaded or released, it should be left to sit for a while and the solution attached to the inner wall will run down before reading. The reader's line of sight must be at the same level as the most concave point of the liquid level in the tube.

If the standard solution is dark (such as KMNO4 solution), the highest part of the concave liquid surface can be read at the same level as the line of sight. If the minimum index is a reading, it should be estimated to read.

4) When the burette is temporarily no longer used after use, it should be washed and wiped clean, and a paper strip should be padded at the live plug to prevent adhesion.

Acidic solution into the alkaline burette Alkaline solution into the acidic burette.

Titration is performed without air bubbles being discharged.

The burette is not rinsed with the solution to be measured.

Readings are not level.

Observe the color change while ** (at this time, you don't need to look at the change of the burette indication), and then read the color change after half a minute (so as not to change the color briefly).

Turn the piston slightly so that the solution hangs over the outlet nozzle to form a half drop, with an Erlenmeyer flask.

Dip it off the inner wall and then use a washing bottle with a small amount of distilled water.

Blow the walls of the bottle. Shake the standard solution in the reagent bottle before filling the standard solution, and close the piston completely when filling. Then hold the upper part of the burette with three fingers of the left hand without scale, the burette can be slightly tilted to receive the solution, and hold the reagent bottle with the right hand to pour the solution into the burette.

The vial can be picked up and poured slowly by holding the belly of the bottle (the bottle stick is facing the palm), and the large bottle can be placed on the table, holding the bottleneck of the bottle and tilting the bottle to slowly pour the solution into the burette until the solution is filled above the zero scale.

Note: When filling liquids, do not use other instruments (e.g., droppers, funnels, beakers).

etc.), be sure to fill it directly with a reagent bottle. Such as standard solution in a volumetric flask.

, it is directly filled by the steak no volumetric flask.

1. Why do you need the same burette for a titration analysis experiment, the purpose is to eliminate the volume difference between different burettes. Because none of the burettes have their own volume calibration curve, it is due to the differences in the production of burets; The use of two burettes and the need to calibrate twice not only consumes time and space, but also introduces new errors.

2. The titration should be started from zero or slightly lower than the zero scale during each titration, because in the titration analysis, the titration volume v of the burette is the difference between the reading v of the titration end point and the "zero scale" vo. i.e. v=v - vo; In this way, the volume error caused by the difference in VO will be eliminated.

During the titration, the burette should be clamped vertically to the burette clamp and the titration table should be white. The burette is about 1 cm away from the mouth of the flask, and the stopcock is controlled with the left hand, the thumb stool is in front, the middle finger of the index finger is behind, and the name finger and little finger are bent at the right angle between the burette and the bottom of the.

When turning the, the fingers are bent and the palms of the hands are empty. Hold the neck of the bottle with three fingers of the right hand, the bottom of the bottle is about 2 3cm away from the table, the lower end of the burette is about 1cm deep into the mouth of the bottle, and the right wrist joint is slightly moved to shake the Erlenmeyer flask, and shake the dripping solution while dripping to mix it evenly.

The standard way of shaking the flask is: hold the neck of the conical bottle with the right hand, and draw a circle along the clockwise direction with the wrist, so that the solution rotates evenly in the flask to form a vortex, and the solution can not beat. The nozzle should be in no contact with the flask.

When the indicator in the flask indicates the end point, the piston is immediately closed to stop the titration. Wash the inner wall of the conical 產. Remove the burette and hold the upper part of the tube with your right hand so that the tube is vertical, and your eyes are level with the liquid level, and read the reading. One person should be estimated at the time of reading.

Basic burette operation method: When titration, hold the burette with your left hand, thumb in front and index finger behind, and use other fingers to assist in fixing the tube tip. Pinch the part of the glass bead with your thumb and forefinger and squeeze the hose forward so that the glass bead is biased towards the palm of your hand, and the solution can flow out of the gap.

The flow rate of the liquid is from fast to slow, at first it can be "drip into a line", then drop it drop by drop, and when it is almost the end, it is added half a drop and half a drop. The method of adding half a drop is to carefully put down the half drop of titration solution and suspend it at the nozzle, lean it down on the inner wall of the conone flask, and then rinse it down with a washing bottle.

When approaching the end of the titration, carefully squeeze out half a drop of the solution so that it hangs on the tip of the tube without dripping, then gently lean it off with the inner wall of the Erlenmeyer flask, and finally rinse the inner wall with water.

Be careful until the droplet hangs on the tip of the burette but does not fall off, and then gently press the Erlenmeyer flask against the tip of the burette to let the droplet fall.

Regarding the operation of the burette, the following burette operation stool is incorrect () aAfter the basic burette is rinsed with distilled water, the prepared EDTA solution is directly added to the 0 scale line to start titration.

b.To read, pinch the upper end of the burette with your index finger thumb and keep the burette weight flush with your eye level with the meniscus plane.

c.Before performing the titration, the air bubbles at the tip of the burette are expelled, the EDTA solution is added to around the 0 scale, and the reading is prepared.

d.The standard for the line of sight to be flush with the meniscus is the integration of the scale marks and the tangent line under the meniscus.

Correct Answer: a

Answer] Before :d filling the titration solution, it is necessary to wash it with the titration solution to remove the residual water in the tube, ensure that the concentration of the dust liquid in the titration difference remains unchanged, pour 5 10 ml each time, and pour it directly into the burette from the reagent Burning Qing belt bottle, without the help of other containers (funnel, beaker peel, etc.).

Answer]: cIf it is an acid burette, the piston can be rotated, and the solution can flow down rapidly to drive away the bubbles. If the alkaline burette is sensitive to lead, bend the rubber tube upward, the glass tip is obliquely upward, and squeeze the glass beads with two bridges or fingers, so that the solution is sprayed out of the outlet tube, and the bubbles escape.

When performing a titration operation, the correct method is ().

a.Look at the position where the liquid level in the burette rises and falls.

b.Eyes on the burette flow locust smile blindly.

c.Keep your eyes on the burette for leaks.

d.The eyes are fixed on the change in the color of the lead air titration solution.

Correct answer: d