Lab Practical

Question 1

What is the first step in starting a titration experiment?

Answer 1

Set up a support stand with a buret clamp, then grab a buret.

Question 2

After obtaining a buret, what is the second step?

Answer 2

check if the buret is clean and if not, clean it with diluted soapy water.

Question 3

Once you have obtained a clean buret, whats the next step?

Answer 3

Pour 50 ml of NaOH solution into a beaker and from there transfer about 5 into the buret to rinse all the water out. After, be sure to fill up the buret with the NaOH solution close to the 0 ml mark

Question 4

What is the mass of citric acid we will need for titrations?

Answer 4

according to the lab manual 0.160 grams

Question 5

Before weighing the citric acid what should we do?

Answer 5

Make sure the weighing tray is clean and completely dry.

Question 6

How do we measure out the citric acid?

Answer 6

After placing it on the balance, we tare it and transfer the product.

Question 7

After we successfully transfer the correct measurement of citric acid, whats the next step?

Answer 7

Transfer the citric acid carefully to the erlenmeyer flask. Make sure you get everything and use some DI water to dissolve the crystals and make sure no crystals are stuck on the side.

Question 8

After adding the citric acid and dissolving it with DI water, what is the next step?

Answer 8

add three drops of phenolphthalein indicator solution to the beaker with citric acid. Begin the titration with the standard NaOH solution until the citric acid solution turns light pink.

Question 9

Once finished, how do we clean up?

Answer 9

Empty all the solutions into the appropriate hazardous waste bins, clean and dry the erlenmeyer flasks.

Question 10

What calculations do we need for the titration of citric acid?

Answer 10

We must calculate molar mass for all trials and find the average and standard deviations.

Question 11

How do we calculate molar mass?

Answer 11

1. find the volume of NaOH used by subtracting final volume of buret - initial volume of buret.
2. find moles NaOH using molarity (multiply average molarity (given) * volume in L)
3. convert moles of NaOH to moles of citric acid using balanced equation (usually 3:1).
4. find molar mass by dividing mass by moles of citric acid.

Question 12

What are the 2 main parts of the limiting reagent experiment?

Answer 12

Making chalk and making copper hydroxide

Question 13

what is the first step in making the chalk for the limiting reagent experiment?

Answer 13

1. using a 100 ml graduated cylinder, measure out 20 ml of 0.5 M CaCl2 into a clean erlenmeyer flask. In another flask, measure out 25 ml of 0.5 M CaCl2

Question 14

What is the second step in makign chalk for the limiting reagent experiment?

Answer 14

In the flask with 20 ml of 0.5 M CaCl2, we will be adding 10 ml of 1.5 M sodium carbonate. To the flask with 25 ml we will add 5 ml of sodium carbonate

Question 15

What should happen after adding and mixing the CaCl2 with the sodium carbonate?

Answer 15

There should be a precipitate,

Question 16

After a precipitate forms, what should be the next step in making chalk for limiting reagent experiment?

Answer 16

Weigh the clean and dry watch glass along with the filter paper.

Question 17

Once the filter paper and watch glass have dried, what is the next step in making chalk?

Answer 17

Set up the vaccum funnel by getting a vaccum flask + hose, buchner funnel, then place the filter paper in the buchner funnel and wet it with DI water

Question 18

What is the most important step about the filter paper?

Answer 18

Make sure it is wet after placing it in the buchner funnel, but not to where water is flowing at the top.

Question 19

After setting up the filter paper and vacuum funnel, whats the next step?

Answer 19

pour one of the precipitates into the funnel, be sure to pour it straight into the middle of the filter paper so you dont lose product. When transferring from the flask, be sure to use DI water to get all the product.

Question 20

How long do we leave the buchnel funnel on for?

Answer 20

20-30 minutes

Question 21

How do we know the precipitate is dry in the buchner funnel?

Answer 21

When it looks like a dry cracked desert

Question 22

After 20-30 minutes and the precipitate is dry, whats the next step?

Answer 22

Remove the filter paper carefully from the funnel and weigh it again with the watch glass.

Question 23

What calculations do we need for chalk?

Answer 23

From molarity, calculate moles of CaCl2 , then convert to moles of Na2Co3.Next, you will need to find theoretical yield by multiplying your values with the mass of CaCl2. From there, to find your expeirmental values, we can find the weight of the product on filter paper (subtracting) and finally, calculating percent yield.

Question 24

For making copper hydroxide, what are the values of drops for each test tube>

Answer 24

1: 4 copper sulfate, 20 of sodium hydroxide
2. 8 and 16
3: 12 and 12
4: 16 and 8
5: 20 and 4