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Aqueous Potassium Bromide

Nitric Acid – Highly Corrosive, poisonous, oxidizing agent

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Silver Nitrate – Poisonous, Corrosive to skin (Wear protecting gloves and/or protective clothing)

Method

1) First pipette approximately 10cm3 of each answer into separate boiling tubes and bubble carbon dioxide into each of the options.

The one goes milky (white precipitate) from colourless is the Calcium hydroxide so this can be eradicated. Label it.

2) The remaining four samples are nonetheless useable for the next test so, add 10cm3 of silver nitrate to all four of the options. One solution ought to give a cream precipitate (Bromide) and one other should give a white precipitate (Chloride).

3) Separate the two samples and to these, add extra ammonia. The one which dissolves is silver chloride. Potassium Bromide and Sodium Chloride have now been eradicated. Label them.

4) The remaining solutions ought to be disgarded (the ones with silver nitrate in) and the remaining two solutions must be put in new boiling tubes (again, 10cm3). Now, to both options add copper (this ought to give a brown gasoline or blue solution.

Nitric Acid has now been eliminated.

5) Add 10cm3 of the one remaining answer to a new boiling tube. The last take a look at is carried out just to make certain that the solution is what we predict it’s, ethanoic acid. Add iron (III) chloride answer should produce a red color. Now label the boiling tube. Ethanoic acid had been eradicated.

Results

Test

Result

Further test

Ca(OH)2 + CO2 –> CaCO3 + H2O

White Precipitate

—–

AgNO3 + NaCl –> AgCl + NaNO3

White Precipitate

Add excess ammonia – Dissolves (more easily)

AgNO3 + KBr –> AgBr + KNO3

Cream Precipitate

Add excess ammonia – Dissolves less easily

Cu + 4HNO3 –> Cu(NO3)2 + 2NO2 + 2H2O

Brown Gas or Blue solution

—–

CH3COOH + FeCl3 –>

Red colour

—–

Bibliography

http://www.angelo.edu/faculty/kboudrea/demos/copper_HNO3/Cu_HNO3.htm

http://www.revision-notes.co.uk/revision/262.html

Part (ii) – Titration

Equipment

Burette

Clamp Stand

Clamp

Burette clamp

Conical Flask

Nitric Acid (Unknown concentration)

Aqueous Sodium Carbonate (0.500 mol dm-3)

Phenolphthalein (a few drops)

Method

1) Set up the apparatus as shown in order that the volumetric flask is sitting on the white tile and the burrette is pointing into the volumetric flask. Make positive that the burette is close to eye stage in order that readings can simply be taken and so that they are correct to 0.1cm3.

2) Pipette 25cm3 of Nitric acid (unknown concentration) into the volumetric flask and add a number of drops of phenolphthalein indicator to the volumetric flask. The answer ought to remain colourless.

3) Fill the burette till it’s on zero (or if barely too much is added, the tap can be used to take it to zero).

4) Carefully and slowly open the faucet and let the nitric acid enter the volumetric flask. The answer will flip pink where the nitric acid is dropping into to sodium carbonate however nonetheless maintain including the nitric acid. When the solution is almost about to alter, start including the nitric acid drop by drop by closing the faucet a till solely a small quantity will get through.

5) Once the solution has turned pink, take a observe of the quantity of nitric acid used (accurate to zero.1cm3.

N.B. Performing the titration greater than once is at all times advised, so the experiment should be repeated a minimal of twice and readings must be inside 0.5cm3.

Calculations

E.g. If 12.2cm3 of nitric acid was used and 25cm3 of sodium carbonate was used then this is how the concentration of the nitric acid could be calculated.

Na2CO3 + 2HNO3 –> 2NaNO3 + CO2 + H20

Moles Na2CO3 = (Volume x Concentration) / 1000

= (25 x zero.500) / 1000

= zero.0125 moles

0.0125 moles Na2CO3 –> 0.0250 moles HNO3

Moles HNO3 = (Volume x Concentration) / 1000

Concentration = (Moles / Volume) x 1000

= (0.0250 / 12.2) x 1000

= 2.049

= 2.05M (3sf)

Also you’ll be able to learn about Ka of ethanoic acid

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