Harcourt Essen Reaction
Making up Hydrogen Peroxide
Volume required 250 cm3 and concentration required 0.1 moldm-3
Given concentration of H2O2 = 1.7 moldm¬-3
Number of moles (n¬¬¬¬¬¬¬¬¬¬¬) = Concentration (moldm-3) x Volume (dm-3)
= 0.1 x 0.25
= 0.025 mol
Volume (dm-3) = Number of Moles (n) X 1000 Concentration (moldm-3)
= (0.025/1.7) x 1000 = 14.7 cm3
Distilled water required: 250 cm3 – 14.7 cm3 = 235.3 cm3
1) Measure 14.7 cm3 of H¬2O2 using a 20 cm3 graduated pipette (with a pipette filler) and transfer to a 250 cm3 volumetric flask.
2) Rinse the pipette filler with distilled water and pour the washings into the volumetric flask.
3) To dilute the solution fill the flask with distilled water until it is 5mm below the calibration line.
4) Use a dropping to add the final quantity of distilled water until the bottom of the meniscus is level with the 250 cm3 mark.
5) Stopper the flask and invert it 10 times to ensure the solution is completely mixed.
The hydrogen peroxide should be stored in a dark and cool place to minimise decomposition, if possible a new solution should be mixed up every time.
Making up Sulphuric Acid
Volume required 250 cm3 and concentration required 0.1 moldm-3
Given concentration of H2SO4 = 4 moldm-3
Number of moles (n¬¬¬¬¬¬¬¬¬¬¬) = Concentration (moldm-3) x Volume (dm-3)
= 0.1 x 0.25
= 0.025 mol
Volume (dm-3) = Number of Moles (n) X 1000 Concentration (moldm-3)
= (0.025/4) x 1000 = 6.25 cm3
Distilled water required: 250 cm3 – 6.25 cm3 = 243.75 cm3
Water added to acid can cause an extremely violent reaction so the acid must always be added to the water. For this reason a ten-fold dilution will need to take place from 40 mol dm3.
n = c x v
= 10 X 0.25
= 2.5 mol
v = (n/c) x 1000
=
Volume required 250 cm3 and concentration required 0.1 moldm-3
Given concentration of H2O2 = 1.7 moldm¬-3
Number of moles (n¬¬¬¬¬¬¬¬¬¬¬) = Concentration (moldm-3) x Volume (dm-3)
= 0.1 x 0.25
= 0.025 mol
Volume (dm-3) = Number of Moles (n) X 1000 Concentration (moldm-3)
= (0.025/1.7) x 1000 = 14.7 cm3
Distilled water required: 250 cm3 – 14.7 cm3 = 235.3 cm3
1) Measure 14.7 cm3 of H¬2O2 using a 20 cm3 graduated pipette (with a pipette filler) and transfer to a 250 cm3 volumetric flask.
2) Rinse the pipette filler with distilled water and pour the washings into the volumetric flask.
3) To dilute the solution fill the flask with distilled water until it is 5mm below the calibration line.
4) Use a dropping to add the final quantity of distilled water until the bottom of the meniscus is level with the 250 cm3 mark.
5) Stopper the flask and invert it 10 times to ensure the solution is completely mixed.
The hydrogen peroxide should be stored in a dark and cool place to minimise decomposition, if possible a new solution should be mixed up every time.
Making up Sulphuric Acid
Volume required 250 cm3 and concentration required 0.1 moldm-3
Given concentration of H2SO4 = 4 moldm-3
Number of moles (n¬¬¬¬¬¬¬¬¬¬¬) = Concentration (moldm-3) x Volume (dm-3)
= 0.1 x 0.25
= 0.025 mol
Volume (dm-3) = Number of Moles (n) X 1000 Concentration (moldm-3)
= (0.025/4) x 1000 = 6.25 cm3
Distilled water required: 250 cm3 – 6.25 cm3 = 243.75 cm3
Water added to acid can cause an extremely violent reaction so the acid must always be added to the water. For this reason a ten-fold dilution will need to take place from 40 mol dm3.
n = c x v
= 10 X 0.25
= 2.5 mol
v = (n/c) x 1000
=