Chemistry Waec GCE EXPOS theory questions

1a the raw materials for the manufacture of synthetic polymeters are readilyand cheaply available from reftining of crude oil
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1d)I)The transition elements are those elements having a partially filled d or f subshell in any common oxidation
1d)ii)trasiction element have variable oxidation states because they do not have incomplete filled D-orbitals
1d)iii)-for conducting electricity
-for making malleable instruments
1cii)
No of mole=mass/molar mass
=1.11/40+(35.5x2)
=1.11/111
=0.01moles/dmcube
20.0g dissolves 0.001moles
Then 1000g dissolves 1000x0.01/20
Solubility=0.05mol/dmcube
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3ai)
Crystallisation is a separation technique that is used to separate. a solid that has dissolved in a liquid and made a solution. The solution is warmed in an open container, allowing the solvent to evaporate, leaving a saturated solution.
3aii)
Evaporation is the process of a
substance in a liquid state changing to a
gaseous state due to an increase in temperature and/or pressure.
3aiii)
Filtration is any of various mechanical, physical or biological operations that separate solids from fluids (liquids or gases) by adding a medium through which only the fluid can pass.
3bi)
i)Their Melting and Boiling Points increases down the group
ii)Their atomic Radius increases down the group
iii)Their Ionization Energy: decreases down the group
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4a)I)HARD WATER:They will not form latter readily with soap.it contains a number of dissolved salts.
Ii)Temporary hardness:Ca(OH)2
Permanent hardness:NaS03
Iii)By using chemicals like caustiic soda. -By using permutot OR zeolite
4b)I)-coagulation/flocculation
-sedimentation
-filtration
-chlorination/disinfection
4b)ii)-potash alum
-iodine
-fluorine
4c)Solubility is the property
of a solid, liquid, or
gaseous chemical
substance called solute to
dissolve in a solid, liquid,
or gaseous solvent.
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