Determine the concentration of sulphuric acid

Diagram

Method

• Set up the stand and burette using clamp allowing enough room underneath for a conical flask.
• Place the funnel into the 50.00cm3 burette. Ensure the burette tap is closed and fill the burette with the aqueous sulphuric acid. Record the initial burette reading.
• Pipette 25.0cm3 of the Sodium Hydroxide solution into a 25.0cm3 conical flask.
• Add 2-3 drops of the Methyl orange indicator to the conical flask
• Run the aqueous sulphuric acid from the burette into the conical flask while swirling the flask.

Verity Reeves                Centre number: 30290                Candidate number: 4733

• Continue adding the aqueous sulphuric acid until the solution turns to a peachy colour.(this is the end point)
• Record the final volume reading on the burette to the nearest 0.05cm3

Repeat experiment until at least two concordant readings are produced for the titre of sulphuric acid. (Titre = final volume – initial volume). Then calculate an average titre.

Calculations – (determining the concentration of H2SO4)

Moles of NaOH = Concentration × Volume

                          = 0.100 × (25.0/1000)

                          = 0.0025

Mole Ratio-

NaOH: H2SO4

         2: 1

  0.0025:

Therefore 0.00125 moles of H2SO4 

Concentration = Moles / Volume

                       = 0.00125 / (Average titre gained in titration / 1000)

[304 words]

Verity Reeves                Centre number: 30290                Candidate number: 4733

Collecting and measuring a gas- Method 2

Apparatus-

• Trough
• Boiling tube
• 50.00cm3 Burette
• Stand and clamp
• Rubber delivery tube
• Weighing boat
• Solid Magnesium Carbonate
• Solution of sulphuric acid (approx  0.05moldm-3)
• 25.0 cm3 Measuring cylinder

Diagram-

Method-

• Fill the trough ¾ full of tap water
• Ensure the tap of the burette is closed.
• Fill the Burette with tap water, place thumb firmly over the open end and turn burette upside down and place the open end under the surface of the water in the trough (burette should remain almost full of water).
• Clamp the burette vertically and upside down, so the end is about 3cm above the bottom of the trough
• Record the initial volume of the burette (readings will be upside down)
• Using a 25.0cm3 measuring cylinder, measure 20.0cm3 of sulphuric acid (approx  0.05moldm-3) and add to the boiling tube.

Verity Reeves                Centre number: 30290                Candidate number: 4733

• Using the weighing boat, measure 1g of MgCO3 and then add to the boiling tube, immediately fit the bung and delivery tube on to the boiling tube.
• Make sure that the end of the rubber delivery tube us placed into the open end of the burette
• Leave for 5 minutes, and then record the final volume reading on the burette.

Repeat experiment until at least two concordant readings are produced for the volume of Carbon Dioxide. (Gas Evolved = initial volume - final volume)

Calculations – (determining the concentration of H2SO4)

1 mole of gas at RTP = 24dm3

Average volume of gas evolved/24000= no. of moles of CO2

Mole Ratio-

 H2SO4: CO2

          1: 1

     

Therefore no. of moles of CO2 is the same as the no. of moles of H2SO4

Concentration = no. of moles of CO2 / (20cm3  / 1000)

[Total: 509 words]

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Verity Reeves                Centre number: 30290                Candidate number: 4733

Calculations for quantities and concentrations used in both methods-

Calculations for Approximate Concentration of H2SO4 and volume of NaOH required in titration- Method 1

H2SO4(aq) + 2NaOH(aq) → Na2SO4(aq)_ + 2H2O(aq)

Aqueous sulphuric acid of unknown concentration approx ~ 10mol dm-3

Aqueous sodium hydroxide concentration = 0.100moldm-3

In the titration I will use a pipette which has a fixed volume of 25.0cm3 of the Aqueous Sodium Hydroxide, in order to use the burette to best efficiency target titre of aqueous sulphuric acid ~ 25.00cm3

Concentration =    Moles / Volume

                           

Moles of NaOH- Volume=25.0 cm3

Moles = Concentration × Volume

          = 0.100 × (25.0/1000)

          = 0.0025

Mole Ratio-

NaOH: H2SO4

         2: 1

  0.0025:

Therefore 0.00125 moles of H2SO4.  Target volume of H2SO4 ~25.00cm3

Approx concentration of H2SO4-

Concentration = 0.00125 / (25/1000)

                        ~ 0.05 moldm3

I will dilute the aqueous sulphuric acid from approx~ 10mol dm-3 to a concentration of approx ~ 0.05 moldm-3

[567 words]

Verity Reeves                Centre number: 30290                Candidate number: 4733

How much MgCO3 and H2SO4 required in evolving a gas- Method 2

MgCO3(s) + H2SO4(aq) → H2O(aq) + CO2(g) + MgSO4(s) 

As I am using a burette capable of containing 50.00 cm3 of gas, my target volume of CO2 evolved is ~ 25.00 cm3/24.00 cm3

1 mole of gas at RTP = 24dm3

24 cm3/24000= 0.001 moles of CO2

Mole Ratio-

 H2SO4: CO2

          1: 1

            : 0.001

Therefore 0.001 moles of H2SO4 (~ 0.05 moldm-3) is needed to produce 24.00 cm3 of CO2

Volume of H2SO4

0.001 moles of H2SO4, I will use the same approx concentration of H2SO4 ~ 0.05 moldm-3 as I have already prepared it.

Volume = moles / concentration

             = (0.001 / 0.05) × 1000

             =20.0cm3

Mass of MgCO3

F.mass of MgCO3= 24.3+ 12.0 + (3 × 16.0)

                             = 84.3

Mass= formula mass × Moles

        = 84.3 × 0.001

        ~ 0.0843g

In order to ensure that all of the aqueous sulphuric acid reacts I will use MgCO3 in excess and so I will use 1g of MgCO3.

[Total words = approx 617]

Verity Reeves                Centre number: 30290                Candidate number: 4733

Reference-

• Indicators -
• A-Level Chemistry, 3rd Edition, E. N. Ramsden page 71-74, Volumetric Analysis
• Cambridge Advanced Sciences, Chemistry 1,