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Calibration of 25 mL pipette

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EXPERIMENT 1 : CALIBRATION OF A 25-mL PIPETTE Introduction Objective : To calibrate a 25-mL Pipette . Method : 1. The weight of the weighing bottle and its cover was taken. 2. The distilled water was transferred in a 25-mL pipette into the weighing bottle . 3. The bottle was weighed and the weighing was repeated until two consecutive readings do not differ by more than 0.005 g. 4. The room temperature was recorded. 5. The volume of the pipette was calculated. Results and calculations : Weight of the bottle and its cover = 49.8813 g Weight of the bottle with distilled water: NO. 1 2 3 4 5 6 7 Weight(g) 74.7011 75.2545 74.7870 74.6905 74.6887 74.6912 74.6918 The average weight of the bottle with distilled water = 74.7864 g Room tempature : 27 � C The weight in vacuum=W The weight in air = Wa=74.7864 g Density of water at 27� C = 0.99654 g mL-1 W = Wa + 1.06 Wa /1000 = 74.7864 g +1.06(74.7864 g)/1000 = 74.8657 g Volume = mass off distilled water/density of water =(74.7864 g - 49.8813)g/ 0.99654 g ...read more.


4.In addition,I need to make sure the tip of the pipette should not immerse too deep into water this is to avoid any mishap during the suction of the water into the pipette via the pipette filler . 5.For future correction,another thing that I should give attention is on how to rinse a pipette: I should : * Fill about half full with Distilled water. * Rotate the pipette while holding it horizontally. Be sure that the water makes contact with all sides. Discard the water. * Repeat the previous two steps with the liquid to be pipetted. * Pipettes are clean if no liquid sticks to the sides after pipetting is completed. If sticking occurs the pipette must be returned for cleaning by the lab technician. 6.On the other hand,when I want to drain the contains to another container,I have to hold the pipette upright until solution has been completely drained.But maybe,on this experiment the liquid did not flow out completely. I cannot blow or force out whatever remains in the tip. ...read more.


2. Between 0.8 to 1.0 g of potassium permanganate was weight and was transferred in a 250-mL volumetric flask,50-mL distilled water was added to the flask ,it was shaked to dissolved the solid,and then distilled water was added to the calibration mark.Some of the solution was placed in the burette. 3. 25-mL of the Sodium oxalate solution was pipette into a 250-mLconical flask .The solution was heated to 80C,and the hot solution was titrated with the potassium permanganate solution.Two times was repeated. 4. The molarity of the potassium permanganate solution was calculated. 5. 10 mLof the potassium permanganate solution was run into a 400-mL beaker and dilute sulfuric acid(1:5) was added to the 100-mL mark. 6. The beaker was warm to 40C ,and then 8mL of nitrite solution was added from a burrete.The tip of the burrete was below the surface of the solution.The tip of burrete was rinse with distilled water.The water was cooled to room temperature. 7. The standart iron(ll)ammonium sulfate solution was placed in a burette and nitrite solution was titrated against it.Two more times was repeated. 8. The molarity of the nitrite solution was calculated. ?? ?? ?? ?? 1 ...read more.

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