P T P4. V

PRACTICAL TASK P4. VOLUMETRIC FLASK Outline Volumetric glassware is manufactured to meet specified levels of accuracy – there are at least two different grades (A & B) and the volume also affects the accepted tolerance. The standard way is to measure the mass of water delivered or contained, with correct use, a number of times. Given that the density of water at different temperatures is well documented (Table 1), the delivered volume can be easily calculated. Procedure 1. Obtain a dry 100 mL B grade volumetric flask and check that it is not dirty inside. 2. Weigh the flask with stopper empty. 3. Fill the flask to the mark as accurately as possible with distilled water and put the stopper in. 4. Weigh again. 5. Measure the temperature of the water. 6. Empty and repeat steps 3‐5 twice more. 7. Determine the density of water at the measured temperature. 8. Calculate the mass of water on each occasion. 9. Using the formula Volume = Mass ÷ Density, calculate the three volumes, and the average value. Reporting Requirements Use the standard Performance Check reporting sheet. The tolerance for a 100 mL B grade volumetric flask is  0.2 mL. TABLE 1. Density of water Temperature (C) Density (g/mL) Temperature (C) Density (g/mL) 18 0.9986 23 0.9975 19 0.9984 24 0.9973 20 0.9982 25 0.9970 21 0.9980 26 0.9968 22 0.9978 27 0.9965