BTEC Applied Science Unit 2 Assignment A - Titration Verified Assignment, Assignments of Social Sciences

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BTEC Applied Science Unit 2 Assignment A - Titration

Unit 2 Assignment A Titration

Introduction

In this assignment I will be going through how I was able to find out an unknown concentration of a

solution using a standard solution to complete a titration. Once completing this I used a pH meter and a colorimeter to find the unknown.

Calibration of pipette, balance and pH meter

Before starting the titration and making the standard solution, I firstly needed to calibrate a few pieces of equipment: the pipette, balance and pH meter.

To calibrate the pipette, you firstly need to gather certain pieces of equipment including, a balance, a small beaker, a larger beaker, thermometer, distilled water, a pipette and a pipette filler. You then

need to rinse all of your glassware with distilled water. Once you have completed the preparation stage, you need to pour some distilled water into the large beaker and place a thermometer in with

the water and leave it until the water has reached room temperature (typically around 200 C) then record the temp. Next, place your empty small beaker onto a balance and record the mass shown.

Now take your pipette with the filler and fill it with water until the meniscus is at the line of the pipette. Next, transfer the water into the smaller beaker you just weighed and record the mass of the

smaller beaker with the water. Repeat this process three times to ensure accuracy. When doing the three trials, enter the data collected into a table that shows mass of beaker + water and mass of only

beaker. With the results you collected, work out the mean mass of water by taking the three masses of water then divide by 3. You then need to calculate the volume of the pipette using the equation:

Volume = Mass x Z value. If the value you get from this equation is the same as the pipette volume, this shows your pipette is calibrated.

To calibrate the balance used in the titration, you firstly need to gather your equipment including a balance, a small screwdriver and a range of masses. In this method I will be using multiple 10g

masses as an example. To calibrate the balance, you firstly need to tare it then place your first 10g mass onto the balance and observe the reading. If the reading is above or below the mass you have

added, use the screwdriver to adjust the values shown. Next add another 10g mass to the one already on the balance and observe the value, again if the value shown is above or below the mass

you have placed, use the screwdriver to adjust the values. Repeat this with multiple masses to ensure the balance is correctly calibrated. This is how you calibrate a balance.

To calibrate a pH meter, you firstly need to gather your equipment including a pH meter, a screwdriver, three beakers, a solution with pH 4 and a solution of pH 9 and distilled water. Firstly,

pour pH 9 solution into a beaker, pH 7 solution into a beaker and distilled water into the third beaker. Secondly, rinse the pH meter with distilled water then place it into the solution of pH 4 but be sure to

keep the meter levitated in the solution. Observe the numbers shown. If the number is below pH 4 use the screwdriver to adjust the values until it reaches pH 4. Do this for the pH 9 solution but make

sure to rinse the meter with distilled water in-between. Once you have completed these steps, rinse the pH meter one more time and the pH meter is now calibrated.

could take place around this equipment. fire breaks out, you should use the appropriate fire extinguisher

The standard solution I conducted was a straightforward procedure, I mixed magnesium carbonate with distilled water to make my magnesium carbonate solution. During the making of the standard

solution the steps I took went well and was completed with no majorly destructive errors however, there were a few errors which could have been avoided if I had better equipment. The first possible

error was that I used a folded paper weighing boat. The weighing boat could have trapped some of the solid magnesium carbonate in the folds which could have meant that the mass of my magnesium

carbonate may not have been 100% accurate. As well as this, the electrical balance I used had an uncertainty of 0.2 which suggests the mass of the magnesium carbonate was not 100% true,

meaning I could have a slightly inaccurate mass.

Titration 1

Equipment list:

• Funnel
• Clamp stand
• Burette
• Four 250cm^3 or above beakers
• Magnesium carbonate solution from standard solution
• Hydrochloric acid
• Distilled water
• 25cm^3 pipette
• PH meter
• Pipette

Method

➢ To carry out this titration you firstly need to set up the equipment such as the clamp stand and any liquids into the appropriate beakers with labels. ➢ Once I've set up the equipment, I poured approximately 100cm^3 of the magnesium carbonate solution into a clean beaker and labelled it ‘magnesium carbonate’. ➢ Now use some of the 100 cm^3 of magnesium carbonate to rinse the burette. ➢ Now fill the burette. ➢ Next, I poured 100 cm^3 of hydrochloric acid into a second clean beaker and labelled it ‘hydrochloric acid’. ➢ Next, I rinsed a 25cm^3 pipette with some of the hydrochloric acid that I previously poured out. ➢ Now add 25cm^3 of hydrochloric acid using the pipette into a 250cm^3 beaker. ➢ Before starting the titration, I took my calibrated pH meter, rinsed it with distilled water. ➢ then place the meter with the 25cm^3 of hydrochloric acid. ➢ Next, I then made sure that I made an appropriate results table. ➢ Now record the starting values of the filled burette. ➢ Now start titrating the contents of the beaker by adding magnesium carbonate from the burette.

➢ For my experiment I recorded the pH every 1.0cm^3 making sure each time I swirled the beaker to mix the solution. ➢ I kept adding the magnesium carbonate from the burette until I reached my end point of pH

➢ I continued to add the magnesium carbonate for my pH curve. Now the titration is finished, you should calculate and record in your results table the volume of sodium carbonate solution used from the end point. ➢ Now calculate the mean volume of magnesium carbonate solution that was used in the titration. ➢ After I calculated the concentration of hydrochloric acid so I could use it in the next titration against an unknown concentration of sodium hydroxide.

Risk assessment

Risk Hazard Precaution Emergency Magnesium Carbonate Could cause serious eye injuries/irritation

Magnesium Carbonate -you must wear eye protection

-Avoid touching eyes after handling

• if in the eye, flood the eye with water for at least 10 mins and consult a medic

-avoid inhaling/ swallowing the solid particles that may be released from the items packaging

-if swallowed, only wash mouth with water and do not try to induce vomiting consult a medic

Could cause harm in the eyes or in an open wound

Hydrochloric acid -You must wear eye protection

-Avoid touching eyes after handling

-if it touches the eyes, flood the eye for 10 mins and consult a medic

-due to its corrosive nature, wear protective gloves if possible

-if ingested, wash mouth out with water

-If spilt on your hands or other skin, completely soak hand with water

Glassware Glass could get broken/smashed; glass could also be stabbed into places such as the hand

-handle the glassware carefully -make sure to not be distracted while handling the glass

-if broken do not touch the glass -if possible, swiftly clean up the broken glass with rubber gloves to avoid further injury Electrical balance Electrocution could Do not touch any If shocked, you should happen or electrical exposed wires and seek advice from a fires could take place make sure any liquids medic and if a fire are handled carefully breaks out, you should around this use the appropriate

for this titration i observed that my results showed that it took a very slow decrease to reach the end

point of pH 7. Due to time constraints I couldn’t use the full 50cm^3 of the burette making it harder for the pH curve as you couldn’t visualise it.

Graph for the results I gathered

Inserted between this page

Calculations for titration 1

4.2 ÷ 84 = 0.05 moles

0.05 ÷ 0.25 = 0.2 mol/dm^3

0.045dm^3 x 0.2 mol/dm^3 = 0.009 mol

MgCO 3 + 2HCL → MgCl 2 + H 2 O + CO 2

0.009 X 2 = 0.

0.018 / 0.045 = 0.4mol/dm^3

Evaluation for titration 1

For this titration I feel that the experiment went well as it was a fairly straight forward procedure, however the experiment was along process and took a while to reach the end point of pH 7 and due

to active time constraints, I couldn’t carry on the titration to assist in drawing the graph or repeat the titration so the reliability of my results was not as good as they could have been. If I was to do this

experiment again and alter the method, I would opt to have a clamp hold the pH meter as during the course of the experiment my hand got tired so I may have accidently touched the edge of the beaker

which could have caused my results accuracy to drop. I would also have more time to complete the experiment. Another alter to the method I would use is to, release the burette tap to intervals of

2cm^3 or 1.5cm^3 to speed up the titration leaving more time to repeat if needed.

Titration 2

For titration 2 I used hydrochloric acid to find the unknown concentration of the alkali sodium

hydroxide. Using a pH meter

Equipment

1. 25cm^3 pipette 2. Funnel 3. 4 beakers 250cm^3 or above 4. pH meter 5. clamp stand 6. Burette 7. Unknown concentration of sodium hydroxide 8. Hydrochloric acid 9. Distilled water

Risk assessment

Hazard Risk Precaution Emergency

Solid sodium hydroxide

Sodium hydroxide solution

Its corrosive nature could cause skin burns and eye damage

Could cause a slipping hazard

-you must wear eye protection

-Avoid touching eyes after handling

-avoid inhaling/ swallowing the solid particles that may be released from the items packaging

• if in the eye, flood the eye with water for at least 10 mins and consult a medic

-if swallowed, only wash mouth with water and do not try to induce vomiting consult a medic

-use smallest amount possible

-if spilt on skin, remove contaminated clothing and drench with water

• if spilt on floor make sure to clean well with water

Hydrochloric acid Could cause harm in the eyes or in an open wound

-You must wear eye protection

-Avoid touching eyes

-if it touches the eyes, flood the eye for 10 mins and consult a medic

ml pH

After completing this titration, this is the maths I used to find the concentration of the HCL and the NaOH.

0.041 x 0.4 = 0.0164 mol

HCL + NaOH → NaCl + H 2 O

0.0264 x 1 = 0.

0.0164 x 0.041 = 0.

Evaluation for titration 2

For this titration I feel that the overall experiment went well with positive outcomes as the

experiment it self was simple and was not misleading or hard to perform. However similarly to titration 1 due to time constraints I could only do this titration once so this made the reliability of my

results not the greatest. If I was to repeat this experiment, I would want to do the titration more times to make it easier to work out means. I also feel that I could have been more careful when

releasing the burette tap as sometimes, I found it hard to stop it at exactly 1cm^3 intervals so this may have caused problems in the accuracy of my results.

Colorimetry

Dilution series equipment

• 0.4M Copper (II) sulphate
• Six test tubes
• Test tube rack
• Two small pipettes
• Distilled water
• Two beakers

Method

Before starting the colorimetry, I first had to make a dilution series using pre made 0.4M Copper (II)

sulphate standard solution. To do this I made different concentrations of copper sulphate in test tubes shown in the table below.

Test tube Amount of water (ml) Amount of 0.4M cuSO 4 (ml) 1 10 0 2 8 2 3 6 4 4 4 6 5 2 8 6 0 10

The steps I took to do this follows as:

1. Pour 100cm^3 distilled water into one of the beakers and 100cm^3 of pre made 0.4M copper sulphate solution into another beaker.

2. I then placed my six test tubes onto a test tube rack
3. I then firstly used a pipette to fill the corresponding amounts of distilled water shown in the table above into each of the six test tubes.
4. Next, I added the corresponding amounts of copper sulphate solutions into the six test tubes.
5. I then made sure to label each test tube to display each amount.
6. Now the dilution series is complete

Colorimetry

Colorimetry is used to measure how much light gets absorbed by the solution which will help us find out what the concentration of the unknown is. For my experiment I used the dilution series to help

me work out the unknown concentrations.

Equipment

As I used the bulk of the equipment in the dilution series, the equipment I needed for the

colorimetry follows as:

• Colorimeter
• Seven cuvettes
• Previously made dilution series
• Test tube rack
• 6 pipettes

Risk assessment

Risk Hazard Precaution emergency Could cause a slipping hazard

Its corrosive nature could cause skin burns and eye damage

Sodium hydroxide solution

you must wear eye protection

-Avoid touching eyes after handling

-avoid inhaling/ swallowing the solid particles that may be released from the items packaging

• if in the eye, flood the eye with water for at least 10 mins and consult a medic

-if swallowed, only wash mouth with water and do not try to induce vomiting consult a medic

-if spilt on skin, remove contaminated clothing and drench with water

• if spilt on floor make sure to clean well with water

Glass could get Glassware handle the glassware -if broken do not

This colorimetry experiment went extremely well and I had minimal problems during both the dilution series and the colorimetry itself. It was straightforward and didn’t face any major issues.

However, due to time constraints I was unable to repeat this experiment. If I could alter the method or re do this experiment, I would opt in changing the ratios from for example 2ml:8ml to 1ml:9ml as

this could have increased the accuracy of my results which in turn will make the accuracy of the unknown concentrations on the graph more accurate as the line of best fit would be better suited to

the results. I would also create a better cleaning system for the pipettes used to prevent cross contamination of the dilution series

References

https://www.youtube.com/watch?v=ELyJu-2jZmE

https://www.youtube.com/watch?v=1REyxt66ZXk

https://www.youtube.com/watch?v=wz0hO1OvbeI