Question

a) Titration of Borax Pipette accurately 10.0 cm of the mixed solution into a 200 or 250 cm conical flask and then add a few drops of methyl red (colour change for this indicator is from red in acid to yellow in basic solution) or screened methyl red indicator. Place this flask on a white, glazed plate available in the lab. Arrange a clean (free from grease) 50-cm burette above the flask and fill this burette with hydrochloric acid (provided) well above the zero mark. Remove the flask from beneath the burette and then drain out the liquid into a beaker or directly into the sink until it is just below the zero mark. Replace the flask with the mixed solution below the burette and then read the initial volume in the burette by aligning your eye with the bottom of the meniscus. You may find that a small sheet of paper with a dark line drawn on it and placed behind the burette with the line just below the meniscus aids in a more accurate reading. Now titrate the mixed solution in the flask against the HCI. This is best done by adding the titrant in increments of about 1 cm and then swirling the solution to ensure complete mixing. Decrease the size of the increments as the titration progresses and near the end point (which is when the changed indicator colour persists for a few seconds) add the titrant in drops. Record the volume in the burette at the end point and so determine the equivalence volume for this titration, which is that required in the calculations. Carry out a rough titration first to get some idea of the end point volume. Do not use the rough titration data when calculating the mean titration (equivalence) volume. The reaction of borax with HCl is: 2 HCI + Na2B4O7. 10H202 NaCl + 4 HBO3 + 5 H20 Note that 2 moles of HCl react with each mole of borax. Calculate the amount of borax present in the mixed solution from these titration data and report the result in terms of g dm on the pro forma provided.

Hello. I was trying to do the question but i think my direction is wrong. Can you help me to solve it please.

Answer 1

This is titration reaction in which one acidic substance neutralizes the other one basic solution. So, the number of moles of acid must be stoichiometrically equal to the number of moles of base. this problem can be easily solved by unitary method. Later on after finding the number of moles mass and amount can be easily calculated but be cautious of units.
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