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Chemistry C4-Chemical Economics
The pH scale and universal indicator:


strong alkali 14 drain cleaner

13 bleach
12 soapy water

11 ammonia

10 milk of

9 baking powder
8 sea water

neutral 7 pure water

6 saliva
5 black coffee

4 acid rain

3 vinegar
2 lemon juice…

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o It can also be used to clean metal surfaces. As a metal surface is usually covered with a
layer of insoluble metal oxide. Sulphuric acid reacts with these, forming soluble metal
salts which wash away.
All metal oxides or metal hydroxides react with acids to form salt and water:…

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Liquid: you lose a bit of the filter paper as it always stays wet
Solid: some will get left behind on the filter paper
Transferring liquids- some liquid will also get left behind on the inside surface on
the old container. (the beakers are always left wet even when you…

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The reaction is reversible- not all nitrogen and hydrogen will convert into
The nitrogen and hydrogen which don't react are recycled and passed through
again so none is wasted.
o Industrial Conditions:
Pressure= 200 atmospheres
Temperature = 450oC
Catalyst= Iron
o Because the reaction is reversible, compromises have to…

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High temperatures usually work the best when washing clothes. As the high
temperatures melt greasy dirt deposits, so your detergent can break up and
remove the stain more easily.
But some natural fabrics shrink and some artificial fabrics quickly lose their shape
if they're washed at too high a temperature.…

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Dry-cleaning can also be used for clothes that have a stain that won't dissolve in
water or detergent. Paints, varnishes and other organic chemicals often dissolve
in an organic dry-cleaning solvent.
Dry cleaning works as the solvent is strongly attached to the oily molecules in the
stain. The intermolecular bonds…

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This also makes graphite slippery and so it's an ideal lubricating material.
Graphite has got a high melting point as the covalent bonds need loads of
energy to break.
Since only three out of each carbon's four bonds are used in bonds, there are
lots of spare electrons. This means…

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Bromide ions will produce a cream precipitate
Iodide ions will produce a pale yellow precipitate
AgNO3 + NaI -> Agl + NaNO3
o Clean water:
o Some communities in developing countries can't get safe water to drink
o They may have to walk for miles to fetch water from…

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3. Divide by the AR of 44.8/56=0.8 19.2/16=1.2
the element
4. Multiply by 10 8 12
Divide by 4 2 3
Empirical formula: Fe2O3

o Electrolysis is the breaking down of a substance using electricity
o Electrons are taken away from ions at the positive electrode (anode) and passed…

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o Question: Find the mass of lead liberated if 5 amps flows for 20 minutes during the
electrolysis of lead (II) chloride (PbCl2)
1. Write out the balanced half-equation for each electrode
Pb2+ + 2e- -> Pb 2Cl- -> Cl2 + 2e-
2. Calculate the number of faradays
First calculate…


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