I am so confused?? I included my data, the procedure and what we need to calcula

Question

I am so confused?? I included my data, the procedure and what we need to calculate. Dont know where to begin. Thank you!

Average mass of Pepto bismol tablets - 1.021

Mass in weighing boat = 10.080 g

Mass of emptied weighing boat = .003

subtract the two masses = 10.077

Measured mass of 2nd filter paper 0.116G

Watch glass 54.756 g

Obtain 10 pepto bismol tablets. Find the average mass of the 10 tablets and calculate the average mass/tablet.   Average mass of pepto bismol tablet = 1.021

Grind the tablets

Pour the contents into a weighing boat and find it mass.   10.080 g

Pour the contents of the weighing boat in a 250 ml beaker and find the mass of the weighing boat after it is emptied. Subtract the two masses for the mass of the ground tablets in the beaker. Mass of emptied weighing boat = .003          subtract the two masses = 10.077

Measure 100 ml of 2 M HCI into a graduated cylinder.

Add 20 ml of 2 M HCI to the powder and mix with a glass rod until it stops foaming.

Using a Buchner funnel, filter paper and a clean arm flash that has been rinsed with purified water, filter the the solution.

if the filtrate is cloudy, pour it back into the beaker and filter it through the same piece of filter paper again.

using your squeeze bottle, rinse the beaker with small amounts of purified water and pour into the funnel. This rinses the solids in the process.

Transfer the solution to 250mL to a volumetric flask.

Use a 25ml volumetric pipette to measure 50 ml of your solution into a beaker.

Measure 60 mL of 0.2 M Na3PO3 in a graduated cylinder and add to the beaker.

using a buchner funnel, filter paper and side arm flask, filter the solution and retain the solid. Filter this solution until clear.

Once your BiPO4 has been filtered, place the filter paper onto a pre weighed watch glass and place it where instructed to dry until next week.

The following week, obtain the mass of the BiPo4 precipitate.

1 Calculate the mass of pepto bismol tablets that were placed into your beaker in step 4 week 1

2 calculate the mass of dry BiP)4 precipitate by subtracting the watch glass and filter paper mass.

from the mass of precipitate, calculate moles of BiPO4 that were formed.

3 Using the moles found in (3) and the knowledge that each sample used 50 ml of solution find the concentration in moles/L of Bi3+ in solution before you added Na3PO4.

4 With the concentration calculated in (4) calculate the total number of moles of Bi in the 250 ml volumetric flask.

5 Knowing that each Bismuth subsalicylate molecule contains 1 bismuth atom (a 1:1 ratio), calculate the number of moles of bismuth subsalicylate you added to your original beaker and convert this to grams.

6 Divide grams of bismuth subsalicylate (6) by grams of pepto bismol used (1). This will give you an answer in units of g Bi-SS/g PB tablet.

7 Knowing your average mass per tablet, find the mass of Bi-SS tablet. Hint you have g Bi-SS g PB and you have g PB tablet.

Explanation / Answer

1. Mass of tablets = 10.080 - 0.003 = 10.077 g

2. You have not given the final mass ( mass of the final ppt in watch glass with filter paper). Let it be X g.

Then, mass of dry Bi(PO)4 precipitate

= X - Mass of watch glass - Mass of filter paper

= (X - 54.756 - 0.116) g

= Y

So, Moles of Bi(PO)4

= Y/ molar mass of Bi(PO)4

= Z mol

3. 10.077 g BiCl3 precipitate ( Bi-SS reacts with HCl to form BiCl3) was taken in a 250 mL volumetric flask. From this 50 mL of the solution was taken in a beaker and Na3PO4 was added to it. we have to calculate the molarity of BiCl3 before adding BiCl3.

We know the no of mol of Bi(PO)4= Z

Now this Bi(PO)4 came from BiCl3 in the solution . The reaction is

BiCl3 + Na3PO4 = Bi(PO)4 + 3NaCl

So, 1 mol Bi(PO)4 comes from 1 mol of BiCl3 . Therefore, no of moles of BiCl3 is also Z mol.

So, 50 mL of the solution contains Z mol of BiCl3.

Concentration in moles/L of Bi3+ in solution before adding Na3PO4

= Z* 1000/ 50

=20*Z moles/L

4. 250 mL of the solution contains

= (20 * Z) * 250/1000

=5*Z moles of BiCl3 .

5. Bismuth salicyalate reacted with HCl to give BiCl3 .

C7H5BiO4 + HCl --> BiCl3 + C7H6O3

1 mol of BiCl3 comes from 1 mol of Bi-salicyalate. So no of moles of Bi-salicyalate

= 5*Z mol

=5*Z* Molar mass of Bi-salicyalate

=5*Z*362.093 g

6. grams of bismuth subsalicylate / grams of pepto bismol used

= 5*Z*362.093 g / 10.077 g

7. mass of Bi-SS in tablet

= (grams of bismuth subsalicylate / grams of pepto bismol) * (Average mass of Pepto bismol tablets)

=[(5*Z*362.093 g / 10.077) * 1.021 ]g

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