NECO GCE Chemistry obj and Theory Questions And Answers For 2018
Electrolytes are the components that conducts electricity in molten form or in solution e.g Nacl solution, CuSO
Electrolysis is the chemical decomposition of a substance brought about by a direct current passing through either a solutions of or a Molten form.
Elements that are electolytically reduced are sodium Na, Potassium, Calcium Ca.
11R and 17S
(i) Na and Cl ==> Sodium Chloride Nacl
(ii) Covalent land
(i) Bleaching Agents
(ii) for making important chemicals such as Hcl
(i) 11R ==> Sodium has low I.E
(ii) Fe (iron) react with cold water to form Iron (iii) tetroxide with the release of hydrogen but slow of the iron not hot
Cold water on sodium, hydroxide forms at first rate but explode with hot water
When water is added to blue anhydrous copper (ii) chloride the colour changes from blue to pink
pOH = 12
LogOH = log base10 -14
Log base10 -14-12
= Log base10 -2
NOTE: dont write base 10 on ur book, instead bring down the 10 under Log.
(I) Oxidizing agents in terms of electron transfer is the loss of electron or an increase in oxidation state of a molecule or an atom or ion
(II) Reduction in terms of change in the oxidation number is the gain of electron or decrease in oxidation state by a molecule, atom or ion.
All halogens are most reactive elements and diatomic molecules which can occur freely in nature
Gay Lussac’s Law of combining volumes states that if gasses react they do so in volume which bears a simple ratios and to the volume of the product. If gaseous provided that the temperature and pressure remains constant
V1 = 250cm3
T1 = 250c
T2 = ?
V2 = 2v1
= 25 + 273
= 2 x 250cm3
V1/T1 = V2/T2
250/298 = 500/T2
250 T2 = 500 x 298
T2 = 500 x 278/250
Atomicity of an element is the total number of atoms present in one molecule of an element or a compound
– Monatomic has –> Helium, Neon
– Triatomic Gas –> Ozone O3
– it is used as antiseptic
– it is in bleaching delicate materials such as Silk, wool, pulp etc
– it is a colourless, odourless gas
– it is neutral to moist litmus paper
– to get the reduction of impurities
– to avoid other constituents to stick to them
CuCO3(s) D–> CuO + CO2
1mole of CuCO3 produce 1 mole of CO2
0.081 mole would give 0.081 moles of CO2
No of mole = mass/molar mass
= 0.081 moles
CuCO3 ==> 123.5
No of mole of CO2 = Volume given/22.4
0.081 = volume/22.4
V = 22.4 x 0.081
Endothermic | Exothermic
(1) heat is absorbed to the surroundings
(2) The Enthalpy change is posture (+ve)
(1) Heat is evolved to the surroundings
(2) The enthalpy changes here is negative
(i) Sodium hydroxide pellets in water is Exothermic
(ii) Ammonium Chloride in water is Endothermic
(iii) Con H2SO4 acid is Exothermic
Saturated Fatty Acids | Unsaturated Fatty Acids
UNDER SATURATED FATTY ACIDS:
– Their bonds to accepts any form of constituents are full
UNSATURATED FATTY ACIDS:
– they still have more bond space so they are Unsaturated
Fatty acid are work acids because they dissociate partially in water and the Hydrogen or Hydroxonium ions are not concentrated
Oxides A B
Mass of Sulphur 7.00g 5.60g
Mass of Oxygen 12.0g 19.1g
20/7* 12 20/5.6*19.1
Allotropy is a phenomenon in which elements exist in various forms having different physical properties but the same chemical properties.
(I) Coal tar and coke
(II) carbon dioxide and water
(i) It is heavier than air
(ii) It does not support combustion
(i) It produces branched chained alkanes which improves octane rating of petrol.
(ii) It requires less amount of energy.
In a tabular form
(i) It is easily reversible.
(ii) No new substance is formed.
(i) It is not easily reversible.
(ii) New substances are usually formed.
(i) It can be separated by physical method.
(ii) Air varies in composition as a result of pollution.
(iii) Air shows the proprties of all the gases present in it.