Determination of some thermodynamic data for the dissolution of Borax Give two p

Question

Determination of some thermodynamic data for the dissolution of Borax
Give two possible sources of error for this experiment.
Cannot be human error, miscalculation Special Considerations Hydrochloric acid can cause burns to the skin or eyes. If you get hydrochloric acid on your skin or in your eyes, wash the affected area with lots of water Boric acid is toxic to humans and can irritate the skin. Wash your hands well after completing this experiment. Procedure: Use a graduated cylinder to measure 5 ml of water into a clean test tube. Mark the water level in the test tube with a Sharpie pen. The test tube will serve as your measuring device for all subsequent work. Place the test tube upside down onto a test tube rack off to the side for later use. Set up a buret, rinse and fill it with standardized hydrochloric acid solution that has been provided. Record the molarity of the acid on your data sheet. Get a clean, dry 100 mL beaker. Place the beaker on a balance, tare it and add about 40 g of borax. It is not necessary to record the weight, since you will be ng this borax to make a saturated solution. Add 50 mL of deionized water to the beaker with borax and stir. It will appear that very little of the solid has dissolved. Place the beaker with water and borax in it onto a hot plate and heat the mixture slowly to about 70°C with frequent stirring. USE A STIRRING ROD. DONT STIR WITH A THERMOMETER While the mixture is heating, place a 150 ml beaker containing about 100 mL. of deionized water onto the hot plate and allow it to heat. Once the mixture has reached 70°C, remove it from the hot plate. Clamp a thermometer so that the bulb of the thermometer is immersed in the saturated solution of borax. 7) Stir the mixture making sure that the solid at the bottom is brought into the liquid phase and then allow it to settle for one minute. 8) Record the temperature of the mixture on your data sheet and then immediately decant some of the test tube to the mark you made. 9) saturated solution into the test tube you marked earlier. Fill the ntitatively transfer the contents of the test tube to a 250 IMMEDIAY and qua mL Erlenmeyer flask. Use the hot deionized water you are heating to wash the test tube. Make sure that the transfer of the borax into the Erlenmeyer flask is quantitative. 10) Add enough deionized water to the Erlenmeyer flask to make the total volume about 25 mL I1) Add 3 drops of methyl orange indicator to the contents of the flask and titrate with HCI. The equivalence point is reached when the indicator turns from yellow to red Record starting and ending buret readings on your data sheet. 12)

Explanation / Answer

Sources of error

(1) The equipments used (such as thermometer, burette etc) are not properly caliberated.

(2) It may happen that the HCl solution was standardized several days ago. So that its present day molarity might differ significantly from the standardized value.

(3) The transfer of contents (borax in water) of test tube to erlenmeyer flask may not be quantitative. Some borax may be stuck to the test tube.

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