Chemistry topic 2 experiments · Web viewTransfer the solution into a 100mL volumetric flask, rinsing the beaker, stirring rod and filter funnel thoroughly with the wash bottle. Fill

Chemistry topic 2 experiments

Perform a firsthand investigation to prepare and test a natural indicator.

Aim: To prepare and test a natural indicator

Hypothesis: If the solution is acidic, then the cabbage juice will turn red

Risk assessment:Chemicals and equipment Risk Minimisation

Bunsen burner Burning yourself Common sense Leave on small of closed

initially, then making the flame bigger later.

Scalpel Cutting yourself Common sense (don’t be silly)NaOH Chemical splashes on the

eyes/skin Goggles Use small amounts

Equipment: Red cabbage leaves/stalks 500mL beaker Conical flask Measuring cylinder Bunsen burner Tripod stand Wire gause Matches Plastic pipette

Filter paper Filter funnel Retort stand Retort ring Boss head HCI (0.1M) NaOH (0.1M) Test tubes Test tube rack

Method:o Break up 2 red cabbage leaves into small pieces and place into a beaker with 300mL of water.o Heat the mixture until it is deep purple.o Filter the mixture to obtain the indicator.o Make up 5 test tubes solutions according to the specifications below and place them each into a separate test

tube.o Place 5 drops of your indicator into each of the 5 test tubes.o Record the resultant colour of the indicator under each test solution in an appropriate table.

Tube Solution pH of solution1 10mL 0.2M HCI 12 0.1mL 0.1M HCI and 9.9mL water 33 10mL water 74 0.1mL 0.1M NaOH and 9.9mL water 115 10mL 0.1M NaOH 14

Results:Tube Solution Colour1 10mL 0.2M HCI Red2 0.1mL 0.1M HCI and 9.9mL

waterPink

3 10mL water Purple4 0.1mL 0.1M NaOH and

9.9mL waterDark green

5 10mL 0.1M NaOH yellow


Discussion:o The indicator was not useful and the results reflected that. This was because there was no standard to compare it

against. It remained the same colour over a range of pHs.o Qualitative test- no numbers used, only used for comparing.o The accuracy of the results was high. The pH meter was calibrated and we knew the exact pH.o The validity of the experiment was high. The method was carried out correctly and the variables were controlled.

The same amount of Acid was added to each beaker of red cabbage juice. The findings relate to the hypothesis.o The relevance of the experiment was that it showed that even natural substances will change colours in different

pHs.

Conclusion:o Natural indicators will produce a given colour when in contact with an acidic substance and different colours when

in contact with a basic substance.


Identify data and choose resources to gather information about the colour changes of a range of indicators.

o Aim:o To determine the pH range for the colour of various common indicators.

o Equipmento Indicators:

Methyl orange Litmus orange Universal indicator Bromothymol blue Phenophyhalein

o

o Sodium hydroxide 0.1Mo Watero 5 x test tubeso Test tube racko 10mL measuring cylindero 5 X 150mL beakers.o Hydrochloric acid 0.1M

o Method1. Make up the 5 test solutions according to the specifications below and place a small amount of each into a

separate test tube.2. Place 3 drops of your indicator into each of 5 test tubes.3. Record the resultant colour of the indicator in each test solution in an appropriate table/colour result.

Test solutionsTube Solution pH of solution1 10mL of 0.1M HCI 12 0.1mL 0.1M HCI + 9.9mL H2O 33 Unknown 54 H2O10mL h20 75 Unknown 86 0.1mL 0.1M NaOH + 9.9mL 117 10mL 0.1M NaOH 14

o Results:Indicator 0 1 2 3 4 5 6 7 8 9 10 11 12 13Methyl orangeBlue litmusRed litmusUniversal indicatorBromothymol bluePhenophtalein natural (red cabbage)

14


Identify data, plan and perform a first-hand investigation to decarbonate soft drink and gather data to measure the mass changes involved and calculate the volume of gas released at 25˚C and 100kPa.

Aim:o To measure the change in mass when a soft drink becomes flat (DE carbonated) and hence calculate the volume

of carbon dioxide released from the drink as it becomes flat.

Hypothesis:o If the lid is opened, then mass will be lost.

Materials:o LA ice colao Electronic balance

Risk analysis:o People may slip due to some of the soft drink falling on the floor.

Method:1. Measure and record the mass of a full bottle of unopened soft drink with the cap on.2. Open the bottle, then close the bottle measuring the mass after.3. Shake the bottle and release slowly ensuring that no mass is lost. Then record the mass.4. Repeat 3 a few times.5. Repeat 1-5 10 times.

Results:Test 1 Jake Test 2 Phil

350.05 351.2348.7 349.1348.1 348.5347.9 348.2

347.85 348.3

1 2 3 4 5346347348349350351

Test 1 Jake

Test 1 Jake

1 2 3 4 5346.5

347.5

348.5

349.5

350.5

351.5Test 2 Phil

Test 2 Phil

Discussion:o Accuracy- Mass was not lost; the same beam balance was used. All the loss was from the carbon dioxide.o Reliability – The experiment was repeated, the results for one brand could not be the same for another.o Validity- The experiment was valid. Evaporation was controlled by closing the lid. An control was used. The bottle

was not in the presence of the sun.

Conclusion:o The bottle was decarbonated and its mass decreased. The loss of 1.2L of carbon dioxide was calculated.

Solve problems and perform a firsthand investigation to use pH meters/probes and indicators to distinguish between acidic, basic


and neutral chemicals.

Aim- To use pH meters or probes to distinguish between acidic, basic and neutral substance Equipment/substances

Safety goggles Gloves 0.1M/L HCI (hydrochloric acid) 0.1M/L NaOH (sodium hydroxide) Universal indicator and colour chart Test tubes and stand or acetate sheet Droppers pH meter

Aspirin Body wash Detergent Vinegar Baking soda Tartaric acid Citric acid pH probe and data logger

Method Using indicators

1. Dissolve any solid household substances in water

2. Dilute any coloured household substance to reduce the colour.

3. If you are using an acetate sheet or similar, place 1 drop of each substance to be tested on the sheet.

4. Add 1 drop of universal indicator to each chemical, being careful not to touch the chemical with the dropper.

Using pH meter or probe and data logger1. Check your pH meter and /or pH probe has

been calibrated.2. Place a small amount of each chemical into

a separate test tube.3. Insert the pH meter and/ or probe into the

chemical and off the ph.4. Wash the pH meter and/or probe with

distilled water before testing the next chemical.

5. Repeat for each household substance.

ResultsSolution tested Readings or observations using Classification

(acidic/neutral/base)pH meter Probe (data logger) Universal indicatorAspirin 6.1 6.09 Yellow/orange acidCitric acid 2.3 2.31 Pink AcidBody wash 5.1 5.29 Red AcidDetergent 7.0 7.14 Yellow BaseTartaric acid 1.5 1.74 Red AcidVinegar 3.0 2.74 Pink AcidBaking soda 7.9 8.15 Aqua Base

Conclusiono pH meters and probes were used successfully to distinguish between acids, bases and neutral substances. It was

shown that citric acid was acidic. Discussion

o The results obtained using the 3 different techniques varied. The universal indicator was the least accurate as only the colour was shown. The pH meter was the second most accurate as it measured the pH to 1 decimal point but the Probe was the most accurate as it measured the pH to 2 decimal points.


Plan and perform a first hand investigation to measure the pH of identical concentrations of strong and weak acids.

Aim:o To measure the pH of identical concentrations of strong and weak acids

Materials1. pH meter and or pH probe.2. Data logger3. Safety goggles4. 50ml of 0.1 solutions of:

HCI CH3COOH C6H8O7

H2SO4

HNO3

Method1. Make 50mL of 0.1M of the acids above.2. Test the pH of the acid solutions using a pH meter/probe.

ResultsName of acid Formula of acid Concentration of acid

(mol/L)Observation pH

Hydrochloric acid HCI 0.1 Red 1.18Acetic acid CH3COOH 0.1 Red 3Citric acid C6H8O7 0.1 Red 2.17Sulfuric acid H2SO4 0.1 Red 1.14

conclusion A substance that is a strong acid has increasing acidity


Choose equipment and perform a first-hand investigation to identify the pH of a range of salt solutions.

Aim:o To make up and measure the pH of identical concentrations of a number of salt solutions.

Hypotheses:o If a salt consists of a strong base and strong acid, it will be neutral.o If a salt consists of a strong base and weak acid, it will be basic.o If a salt consists of a strong acid and weak base, it will be acidic.

Materials 100mL volumetric flask Electronic balance Various salt samples Deionized water

Stirring rod Filter funnel Beaker Universal indicator

Method1. Calculate the mass of the salt needed to make up 100mL of an 0.1M solution.2. Weight out that mass of the salt into a clean beaker.3. Dissolve the salt in a minimum amount of deionized water in the beaker4. Transfer the solution into a 100mL volumetric flask, rinsing the beaker, stirring rod and filter funnel thoroughly

with the wash bottle.5. Fill the volumetric flask up to the 100mL line with deionized water. Ensure that the bottom of the meniscus is on

the line.6. Stopper and invert the flask several times to mix the solution thoroughly.7. Add 50mL of the solution to a clean beaker.8. Using the pH probe and data logger, record the pH of the solution.9. Add 4 drops of universal indicator to the beaker. Record the colour.10. Gather the data for all the other salts.

ResultsName of acid Formula of acid Parent (origin) acid and base (strong

or weak)Predicted pH Measured pH

Sodium chloride NaCI Na=strong base, CI = strong acid 6.43Sodium acetate CH3COONA Na=strong base, CH3COO- = weak acid 8.23Sodium carbonate Na2CO3 Na =strong base, (CO3)2+ = weak acid 11.06Sodium hydrogen carbonate NAH(CO3) 8.33Potassium nitrate KNO3 K= strong base, NO3

- =strong acid 7

Ammonium chloride NH4CI NH4= weak base, CI= strong acid 6.23Zinc chloride ZnCI2 5.93Barium chloride BaCI2

Magnesium sulfate MgSO4

Discussion The experiment was invalid due to the use of impure salts. The variables were controlled; volumetric flasks and

calibrated scales were used. It measured the ph. The validity could be improved be using deionized water, using pure salts and more precise equipment.

The reliability was low as there was no repetition, no average pH and series of results.

Conclusiono If a salt consists of a strong base and strong acid, it will be neutral.o If a salt consists of a strong base and weak acid, it will be basic.o If a salt consists of a strong acid and weak base, it will be acidic.


Perform a first-hand investigation and solve problems using titrations and including the preparation of standard solutions, and use available evidence to quantitatively and qualitatively describe the reaction between selected acids and bases.

Part A: Making a primary standard Aim:

o To use anhydrous sodium carbonate (Na2CO3 ) to make a primary standard.

Materials


Pure anhydrous sodium carbonate (Na2CO3 ) Accurate balance Watch glass Wash bottle filled with distilled water Extra distilled water

250mL volumetric flask 250mL beaker Stirring rod Filter funnel Dropper Safety glasses

Method1. Decide the approximate concentration needed for the sodium carbonate solution.2. Decide how much solution will be needed.3. Calculate the amount needed to weigh out to get mLs of mol/L solution.

calculationsSodium carbonate solution = 0.05M/LAmount of solution = 250mln=Concentration x volume∴n=0.05 X 0.25=0.0125

n= MassMolar mass , ∴ M=0.0125 x105.99=1.32g /250mLg/L ¿1.32x 4=5.28 g

Discussiono There were problems in carrying out the experiment as in the bulb pipette, the level of solution did not stay

constant.o Sodium carbonate was suitable as the primary standard as the exact composition can be found, there is a high

level of purity, and a high molecular weight.

Conclusiono We made 5.32 ml of a standard solution of sodium carbonate with a concentration of 0.0528 moles per

litre.Part B: titrating the primary standard against hydrochloric acid.

Aim:o To determine the exact concentration of a solution of hydrochloric acid by titrating it against an already made

solution of sodium carbonate.

Materials Safety glasses Primary standard solution (0.05M Na2CO3 ) 0.025M Hydrochloric acid Indicator (methyl orange) White tile/paper

Burette Burette stand and clamp Pipette Pipette filler Conical flask

Risk assessment:o Wear safety glasses as HCI may fall into your eyes during the pouring of

the acid.

Method1. Check all equipment is clean and rinse the conical flask with distilled

water.2. Rinse the burette and pipette with the solution to be used in each. (HCI =

burette, pipette = Na2CO3 )3. Set up the burette in its stand. Check it is vertical and the tap is off.4. Pour HCI through a funnel into the burette and take a reading.5. Pipette 25mL of the standard (Na2CO3) into a conical flask.6. Place a white tile/paper under the conical flask so the colour change can

be seen.7. Add 3 drops of the indicator to the conical flask.8. Adjust burette until the tip is just inside the top of the conical flask.9. Slowly add HCI to the conical flask.


10. Stop as soon as there is a permanent colour change in the colour of the indicator.11. Read the level in the burette.12. Repeat steps 4 to 12 until you have 3 titres (amount of acid used) within 0.1M of each other.13. Calculate an average and calculate the concentration of the hydrochloric acid.

Results

Attempt no. 1st reading of burette (mL)

Final reading of burette (mL)

Volume of acid used (titre)(m/L)

1 (rough) 0.1 24.7 24.6

2 0 23.5 23.5

3 0 23.5 23.5

4 0 23.5 23.5

Average 0 23.5 23.5

Na2CO3 + 2HCI → 2NaCI + H2O + CO2

Calculationsn(Na2CO3)= 0.05 x 0.025 = 0.00125n(HCI) = 2 x n(Na2CO3)n(HCI) = 2x 0.00125= 0.0025mL

C(HCI)= nv= 0.00250.02356

= 0.106m/L

Na2CO3 HCIn 0.00125 0.0025C 0.05m/L 0.106v 0.025L 0.02356

Discussiono Repetition of the titration increases the reliability of the experiment results.o The hydrochloric acid can be used as the secondary standard as the solution was accurate.o The results were accurate as the results were close to the published result and the correct equipment was used.o The reliability of the results were high as they were within 0.1ml of each other. To improve the reliability, everyone

should have used the same standard solution.o The validity was high as the experimental method was followed exactly, the equipment was rinsed with the

solutions that were going into them and the variables were controlled.

Conclusiono We titrated hydrochloric acid against a standard solution of 0.5 mol/L sodium carbonate solution and found

experimentally that the concentration of the hydrochloric acid was 0.106 mol/L

Part C: using a secondary standard Aim

o To use a previously standardized solution of HCI as a secondary standard in a titration to determine the concentration of a solution of sodium hydroxide.

Materials Safety glasses Secondary standard ( 0.106 mol/L HCI White tile

Indicator (methyl orange) Burette Burette stand and clamp. Conical flask


Risk assessment:o Wear safety glasses as HCI may fall into your eyes during the pouring of the acid.

Method1. Check all equipment is clean and rinse the conical flask with distilled water.2. Rinse the burette and pipette with the solution to be used in each. (HCI = burette, pipette = NaOH )3. Set up the burette in its stand. Check it is vertical and the tap is off.4. Pour HCI through a funnel into the burette and take a reading.5. Pipette 25mL of the standard (NaOH) into a conical flask.6. Place a white tile/paper under the conical flask so the colour change can be seen.7. Add 3 drops of the indicator to the conical flask.8. Adjust burette until the tip is just inside the top of the conical flask.9. Slowly add HCI to the conical flask.10. Stop as soon as there is a permanent colour change in the colour of the

indicator.11. Read the level in the burette.12. Repeat steps 4 to 12 until you have 3 titres (amount of acid used) within

0.1M of each other.13. Calculate an average and calculate the concentration of the hydrochloric

acid.

Results

Attempt no. 1st reading of burette (mL)

Final reading of burette (mL)

Volume of acid used (titre)(m/L)

1 (rough) 0.4 2.8 2.4

2 2.8 4.151.35

3 5 6.3 1.3

4 78.3 1.3

Average 4.38mL 6.25mL 1.32

NaOH + NaOH → 2NaCI + H2OCalculations

n(HCI)= 0.025 x 0.106 = 0.000265n(HCI) = n(NaOH)n(NaOH) = 000265

C(NaOH)= nv=0002650.0013

= 2.03Mol/L

NaOH HCIn 0.000265 0.000265C 2.03Mol/L 0.106v 0.0013L 0.025

Perform a first-hand investigation to determine the concentration of a domestic acidic substance using computer-based technologies.

Part 1 – making the primary standard Aim:

o To use anhydrous sodium carbonate (H2C2O4. H2O ) to make a primary standard.


Materials Pure hydrous oxalic acid (H2C2O4. H2O ) Accurate balance Watch glass Wash bottle filled with distilled water Extra distilled water

250mL volumetric flask 250mL beaker Stirring rod Filter funnel Dropper Safety glasses

Method1. Decide the approximate concentration needed for the oxalic acid solution.2. Decide how much solution will be needed.3. Calculate the amount needed to weigh out to get 250mLs of 0.05 mol/L solution.4. Dissolve the oxalic acid in a 250mL beaker using a glass rod to stir. Add the water up to 250 mL.5. Transfer the solution to a clean 250mL volumetric flask via a glass rod. Make sure to read from the meniscus.

CalculationsOxalic acid solution = 0.05M/LAmount of solution = 250mln=Concentration x volume∴n=0.05 X 0.25=0.0125

n= MassMolar mass , ∴ M=0.0125 x126.07=1.58 g/250mLg/L ¿1.58 x 4=6.32g

Part 2 – preparing the secondary standard Method

1. Decide the approximate concentration needed for the sodium hydroxide solution.2. Decide how much solution will be needed.3. Calculate the amount needed to weigh out to get 250mLs of 0.05 mol/L solution.4. Dissolve the sodium hydroxide in a 250mL beaker using a glass rod to stir. Add the water up to 250 mL.5. Transfer the solution to a clean 250mL volumetric flask via a glass rod. Make sure to read from the meniscus.

Calculationssodium hydroxide solution = 0.05M/LAmount of solution = 250ml`n=Concentration x volume∴n=0.1 X 0.25=0.025

n= MassMolar mass , ∴ M=0.025 x39.998=1g /250mLg/L ¿1 x4=4 g/L

Part 3: determining the concentration of acetic acid Aim: To determine the acetic acid concentration of household vinegar.

Equipment:

Ph probe 25mL pipette 50mL burette 250mL volumetric flask Retort stand Burette clamp

Vinegar Distilled water Filter funnel Phenolphthalein indicator Wash bottle Pipette filler 0.0985M standardized NaOH (secondary solution)

Method:1. Clean a 25mL bulb pipette by rinsing with vinegar.2. Add 25mL of the vinegar to a clean and dry 250mL volumetric flask, using a bulb pipette and dilute to 250mL with

distilled water.3. Add 25mL of the diluted vinegar solution to a clean and dry beaker.4. Add 3 drops of indicator to the vinegar solution.5. Set up the pH probe and data logger. Place into the beaker. Record the pH.


6. Clean a burette with the standardized solution of NaOH.7. Set the burette up on the retort stand and burette clamp.8. Run a small aliquot of NaOH into the beaker . Record the volume added and the pH.9. Repeat step 8 until a permanent colour change persists.

Results

Volume of NaOH added

PH of solution

Volume of NaOH added

PH of solution

0 3.44 20.2 9.381 3.77 20.3 9.652 4 20.4 9.813 4.16 20.5 10.034 4.29 20.7 10.335 4.42 20.9 10.496 4.51 21 10.637 4.62 21.2 10.88 4.7 21.6 10.969 4.77 22 11.08

10 4.86 22.5 11.2211 4.95 23 11.3212 5.03 23.55 11.4213 5.12 24 11.4814 5.22 24.5 11.5415 5.34 25 11.5816 5.46 25.5 11.6317 5.63 26 11.6618 5.82 26.5 11.7119 6.16 27 11.7420 7.18 30 11.88


Identify data, plan, select equipment and perform a firsthand investigation to prepare an ester using reflux.

Aim:o To identify data plan, select equipment and perform a firsthand investigation to prepare an ester using reflux.

Risk assessment:Chemicals and equipment Risk MinimisationAlkanol (pentanol) Slightly toxic

Flammable Skin and eye protection Well ventilated area

Concentrated sulfuric acid Highly toxic Considerable heat

Eye and skin protection Use small quantities Always add water

Hot plate Considerable heat Use plastic clampsAcetic acid Highly skin irritant

Highly corrosive Small quantities Well ventilation

Materials Alkanol (pentanol) Alkanoic acid (acetic acid) Reflux equipment

1. Rubber hoses2. Round bottom flask3. Condenser

Retort stand Boss head and clamp sodium carbonate

Sulphuric acid Boiling chips Water bath Large beaker Electrical hot plate Measuring cylinders

Method1. Set up the equipment like the diagram to the right.2. In a fume cupboard measure out 20 ml of pentanol into a dry, round bottom flask.3. In a fume cupboard measure out 10 ml of acetic acid into a dry, round bottom flask. Note the smell

of the mixture.4. In the fume cupboard, have the teacher add 2mL (40 drops) of Conc sulfuric acid to the

alkanol/alkanoic acid mixture in the round bottom flask.5. Before beginning to heat the flask, ensure the water is flowing through the condenser (in the bottom

of the condenser and out the top)6. Heat the flask for 30 minutes, maintaining reflux, so that no vapours are

lost.7. Stop heating and allow the flask to cool. Carefully disassemble the

apparatus. Pour the refluxed mixture into the separating funnel.8. Add sodium carbonate solution to the flask.9. Compare the smell of the products to the reactants.

Discussion Write a balanced equation shat shows the esterification.

C5H11OH + CH3COOH ↔ CH3COOH11 + H2O Pentanol + Acetic acid ↔ pentyl acete

Why was the reaction refluxed?


Refluxing prevents a loss of volatile products or gases. It also allows higher temperatures to be reached.

Why was sodium carbonate used to purify the ester? What will it react with? Sodium carbonate reacts with the remaining acetic and sulfuric acid, thus eliminating them from the

ester.

Explain how the catalyst affects the equilibrium and the rate of reaction. The catalyst absorbs the products and water, thus shifting equilibrium to the right. In addition, the rate of

reaction increases.

In the commercial production of esters, either the acid or alcohol is reacted in large excess. Explain why, using La Chatelier’s principle.

La chatelier’s principle, states that when a system is disturbed, the equilibrium will shift in the direction that will counteract that change. More esters will be produced to get rid of the extra acid/alcohol.

Conclusiono

Documents

Chemistry topic 2 experiments · Web viewTransfer the solution into a 100mL volumetric flask, rinsing the beaker, stirring rod and filter funnel thoroughly with the wash bottle. Fill