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* PAGE 1 * PAGE 2 * PAGE 4 * PAGE 5 * PAGE 6 * PAGE 7 * PAGE 8 * page 9 from the Futures Language School, Cairo * EMAIL Dr Mahmoud Marsafy * back to Dr M's index * doc b email query?comment REMEMBER: you must do your own experiment risk assessment, ideas are illustrated but health and safety details are NOT included 14. The water of crystallisation of Copper(II) Sulphate 1 6 15. Simple distillation to purify water (illustrated using copper sulphate solution)
16. Models of methane, ammonia, water, hydrogen chloride and the formation of ammonium chloride
17. Simple salt hydrolysis experiments and the acidity of the hexaaqua aluminium ion [Al(H2O)6]3+
18. GAS PREPARATIONS Chart
1 Set up for preparation of
gases:
§
The
vial rubber stopper is pierced and a pipette tip is firmly inserted and a
convenient length of the gas delivery
narrow plastic tube is fixed to its tip. §
The
appropriate reactants are added into the gas generating vial which is then
immediately stoppered. It may be heated (if required) with the flame of a
spirit burner or on a hot plate. §
Collection
of gases above water in an inverted test tube (if appropriate), is facilitated
by securely positioning the gas delivery tube with a tissue paper plug before
inverting the tube. Thus it is
very easy and convenient to
achieve initially a completely filled inverted tube without any air bubbles. §
If
needed gradual addition of a solution reactant may be achieved by injection
through a syringe needle inserted into the rubber plug. Charts 2 and 3 Heat Decomposition of Lead Nitrate and collection of NO2 gas.
§
Several
samples of NO2 may
be collected by consecutive replacement of collection vials and immediately
stoppering each vial once filled with NO2 gas. §
There
is minimal gas escaping to the air, thus there is no need to operate this
procedure in a fume hood. But it is recommended to operate in a well
ventilated environment. Of course the other basic safety precautions must be
practiced. Charts
4
and 5 NO2 &
NO gases
§
A
small length of very thin copper wire is used. Brown
NO2 is
immediately generated on addition of drops of colorless concentrated Nitric
Acid. The reacting mixture simultaneously
acquires a greenish colour [Cu(NO3)2]. §
The
gas generated when using dilute Nitric Acid is colorless NO. §
The
upper inverted vial containing NO is slightly lifted, allowing some air into
the vial, thus causing the reaction producing NO2.
§
NO2 gas
, being heavier than air is readily collected by downward delivery . §
Conventional
preparation setups (from published literature) are included for comparison
with the microscale technique presented. §
The
bead model for the NO2 molecule
prominently demonstrates : The
dative bonding, and **
The single nitrogen non-bonding
electron leading to an O-N-O
angle of 134
deg. This single
non-bonding electron is the cause of the ready dimerisation to the colorless N2O4
gas. * PAGE 1 * PAGE 2 * PAGE 4 * PAGE 5 * PAGE 6 * PAGE 7 * PAGE 8 * page 9 from the Futures Language School, Cairo * EMAIL Dr Mahmoud Marsafy * back to Dr M's index * doc b email query?comment
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