2016 WAEC GCE CHEMISTRY OBJECTIVE AND ESSAY NOW AVAILABLE

Chemz Obj

1ADCAADAADA

11DDDBBDDDCC

21CBBACBADAD

31CACCBDDADB

41CDBCDBCCBA

(2ai)

Vander waal's force are weak intermolecular gases at room temperature.

(2aii)

-Electronegativity difference

-Ionization energy

(2aiii)

-Ionization energy

-Electron affinity

(2b)

C-F and C-O

C-N and C-H-O and C-N and C-F and C-O

(2ci)

-Be=1S^22S^2

4Mg=1S^22S^22P^63S^2

They both have the same number of electron in the outermost shell

(2cii)

Mg^2+->Na^+->Ne

The size of positive ion is less than that of the neutral atom

(2bii)

C-F>C-O>C-N>C-H(order of polarity).

(2ci)

4Be=1S^2 2S^2

12mg =1S^2 2S^2 2P^6 3S^2.

(2cii)

4Be and 12Mg have similar chemical properties because they belong to the same group in the periodic table. Both 4Be and 12Mg belongs to group II in the periodic table hence they have similar chemical properties.

(2di)

Transition element: Transition elements are those element with partially or incompletely filled d-orbital. Transition metal form coloured ion (or compound), they acts as catalyst,they have variable oxidation stat, they are paramagnetic, they form complex compound or coordination compound

(2dii)

Most transition metals have variable oxidation state because they undergo bonding with the electron in the ns and (n-I) d-orbital .e.g. most of the first series of transition metal from scandium to Zinc have variable oxidation state because they undergo bonding with electron in 4s and 3d- orbital.

(2diii)

(i) Metals are used in electroplating

(ii) Metals are used in making electronic cables and cooking utensils because they are good conductor of heat and electricity.

(2div)

It is used in electroplating and galvanizing to make electrical cable

4ai) 

Hard water is water which does not lather readily with soap. Hard water is formed when water percolates through deposits of limestone and chalk which are largely made up of calcium and magnesium carbonates.

(ii) 

-Temporary hardness: Ca(HCO3)2

-Permanent hardness: Na2C03

(iii)

-By using chemicals like caustiic soda.

-By using permutot OR zeolite

(4bi)

(i) coagulation

(ii) sedimentation

(iii) filtration

(iv) chlorination/disinfection

(4bii)

(i) Sodium chloride

(ii) Potassium chloride

(iii) Chlorine dioxide

(4ci)

Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent

.

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

3c)

3di)

Le Châtelier's principle, states that if a system in equilibrium is disturbed by changes in determining factors, such as temperature, pressure, and concentration of components, the system will tend to shift its equilibrium position so as to counteract the effect of the 

3dii)

3e)

dynamic equilibrium is a steady state

reached when a reversible reaction occurs at the same rate in both directions and has an unchanging ratio of products and reactants