nternet. Athogh erors in buret and pipet markings by the manefacturer are usuall

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nternet. Athogh erors in buret and pipet markings by the manefacturer are usually small, they cannot be neglectecd Experimental Instructions 1 ) RESALLDIRECOS balances and volumetnic glasswae. A basic review can be found on the class Blakboard, and ASK questions if you are unsure Make sure you understand the proper use of the analytical 2) Befone you begin, make sure you glassware is CLEAN Water should run out smoothly, leaving thin film on the inside of the glass. It should not "bead" on the inside. Be sure lo note the type of the glasware before calibration 3) e about 80 mL ofdeionued water in a 1000 mL beaker with a thenhometef tomperature of the water to oquilibrate to room temperature. Record the water temperature Why s this importan Allow the 4) Note the specification given for the maximom weight allowance of the balance Why is this ) Perform the buret calibration Fill buf with DI water and remove air bubbles bom the water column and tip by daining the buret. If you see any water beads form in the buret, clean the buret and start over Refill the buret so the meniscus is just under 0.00 mL a) b) cUsing gloves peeweigh a 125 ml flask giving the water in the buret time to settle. If there is a drop in the water level tightem the stopcock and allow the water to sk again and recond the final liqaid lkvel. (Why must gloves be wom?) d Deain-10 mL of water into the pee-weighed flask slowly, Allow 30 scconds for the 61m of liquid on the outer walls to desoend, rocond the new liquid lvel (Find the amount of liquid delivered by difference) e) Weigh the flask again to determine the mass of water deliverod g) Repeat the draining and weigeing for-30mL-40mL and-0mL (Make sure to not mas h) Repeat steps b thoough g with the same buret If you need more detail you can find i) Calculatxes the .n-laboratory worksheet due at the end of lah, fillin the appropriate data Drain the bunet from-10mL to-20mL and repeat steps d &e out the scale, you will lose a data point. How do you insune this does not happen instructions at the end of Hanis chapter 2 and construct a plot similar to Figure 3-3: Calibration curve for a 50-mL. Baret. If your two buset runs are not show ing a trend, should you calibeate the buret a thind time? Consider what laboratory you are enrolled i 6) Perform the 25 mL Volumetric Flask Calibration: a Weigh the clean and dried volumctric flask to the nearost milligram on an analytical balance b) Fill the flask with distilled water from step 3 to just below the 23 mL mark c Carefully add water with a disposable pipet until the botom of the meniscus coincides with the calibration linc. Remove droplets of water pecsent above the line with a lint-less Kimmipe d) Reweigh the flask and secord the mass. c) Immediately affer weighing, measure and record the temperature of the water in the flask if not using water from stop 3 Calculate the true volume coata ned in the volumetrK nk by usang the difierence in mas and temperature correction Obtain at least three measurements by emptying the flask and drying it between measurements. Air drying is best it' time permits, DO NOT use the house ar lines (Why?) If you are careful in keeping rack ef your glassware you can allersate glassware weighings to help in the drying process I) 7) Perform the 30 ml beaker and 25 mL Erlenmeyer Mask calibeations a) Place a clean, dry beaker or Erlenmeyer on the lab scales and rocoed the mass in your lalb b) Remove the beakcr ask from the balance and add soee of the DI water then use the disposablk pipet to get the meniscus as close to the 25 mL gradution mark on the beaker flask read and record the volume of water c) Place the beaker lask on the same scale. Calculate (by saltracting the mass of the empty beakerflask) and recoed the mass of the water contained in the beakenhask d)TARE the scales and repeat Soe trials 2 and 3 (up the frve trials) using the samc beaken lask Page 2 of4

Explanation / Answer

3 .It is necessary to equilibrate the water to room temperature , because the clear view will be given at room temperature.

4 . The weight more then the max. allowance will show error in weighing and will not be accurately measured .

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