Note the tubing is to allow the contents of the ignition tube to come out and react with the sulphuric acid.
The chemical equation for this reaction is
Mg + H2SO4 → MgSO4 + H2
From this reaction I will be measuring the amount of H2 that is being produced, I expect that to be around 70cm3 seeing as the gas syringe can hold up to 100cm3. To calculate how many moles of hydrogen I have collected I must use the rule that any gas is 24dm3
Firstly I must convert the cm3 → dm3 by dividing 70 by 1000
70 ÷ 1000 = 0.07dm3
Secondly I need to divide the 0.07dm3 by the 24 litres using the rule.
0.07dm3 ÷ 24l = 0.002916 moles
I must now calculate how much of the Mg I need to react with the H2SO4, I will do this by using the molar ratio which is 1:1 which means this will also be 0.002916 moles to work this out in grams I need to times by the Mr of Mg which is 24.3
0.002916 x 24.3 = 0.070874g which is roughly 0.07g
I will weigh this much of Mg use electronic scales which have an accuracy of 0.01g.
To calculate the % error I must do the accuracy of the equipment over the mass of the Mg times 100
(0.01 ÷ 0.070874) x 100 = 14% (This is an estimate)
If I was using a more accurate method of weighing the mass using scales that had and accuracy of 0.001g I’d have a lower % error.
(0.001 ÷ 0.070874) x 100 = 1.4% (This is an estimate)
I now need to calculate the minimum volume of H2SO4 required to produce 0.002916 moles of H2. Using the molar ratio of 1:1 I know I need 0.002916 moles of H2SO4. To work out the volume I will use the formula
Volume = Moles ÷ Concentration
(The initial concentration of H2SO4 is 1moldm-3)
0.002916 ÷ 1 = 0.002916
0.002916 x 1000 = 2.916cm3
For the actual experiment I will use 5cm3 of the H2SO4 to ensure there is excess acid to react with the Mg (0.07g).
To prove that the H2SO4 is dibasic I am going to use the ionic equation which is
2H+ + 2e- → H2
This is in consideration that I have collected approximately 70cm3 of H2 gas, I can show that I have collected 2 moles of H2 gas.
Titration
For the second experiment I am going to be reacting H2SO4 with NaOH with the equipment listed below
Conical Flask
Burette
Pipette
Beaker
Electronic Scales
Distilled Water
The equation for this reaction is H2SO4 + 2NaOH → Na2SO4 + 2H2O
- Test for ethanoic acid.
Firstly you must warm ethanol with the ethanoic acid in presence of a strong acidic acid to form ethyl ethanoate and water which produces a sweet smelling ester. The actual test is to waft the reactants and if you smell something sweet an ester has been formed and you have found ethanoic acid.
- Test for cyclohexene
- When testing for cyclohexene you must add orange bromine water to the solution that you think is cyclohexene as the cyclohexene will de colourise the bromine water this is an addition reaction.
-
Test for bromoethane
The bromoethane must first be warmed with some sodium hydroxide solution in a mixture of ethanol and water. In this reaction the halogen atom will be displaced to a halide ion. Now you must acidify the mixture by adding dilute nitric acid as this prevents unreacted hydroxide ions reacting with the silver ions. Then silver nitrate solution is added. Various precipitates may be formed from the reaction between the silver and halide ions. To check that you have got bromoethane a very pale cream precipitate will have formed
-
Test for butan-1-ol
To test for a primary alcohol you must oxidise the alcohol by heating with acidified aqueous potassium dichromate (VI), on gentle heating the primary alcohol will produce aldehydes . While the aldehyde is formed it must be separated by distillation as they are formed seeing as their more volatile than their corresponding alcohol. Upon stronger heating under reflux with an excess of acidified dichromate (VI), they aldehydes are oxidised to carboxylic acids. To see if you have a primary alcohol you would notice a distinct change to a very dark shade of brown/green.
- Test for 2-methylpropan-2-ol
To test for this secondary alcohol you would add a couple of drops of the alcohol into a test tube containing potassium dichromate (VI) solution acidified with dilute sulphuric acid. The tube would be warmed in a hot water bath. After heating over a sufficient period of time the tertiary alcohol should turn orange.