WAEC GCE JAN/FAB 2019CHEMISTRY
waec-gce-2019-commerce
The
SUBJECT IS: Waec Gce Chemistry ANSWER'S
CHEMISTRY OBJ:
1-10: BDABADDCAA
11-20: DDBABDBBCC
21-30: -DA
waecgce-2019-literature-in-english
(4ai)Hardness of water is a situation where by water does not lather well with soap which is causes by dissolution of some salts like CaSO4 and MgSO4 in the water.
(4aiii)(i) It causes furging of kettles and boilers.
(ii) It causes waste of soap and water.
(4bi) Ammonia NH3, OxygenO2
(4bii) Ammonia is poured over heated platinum rhodium catalyst at 700°c to produce NO and steam which then in the presence of excess air gives NO2. It is then sprayed with hot water to formHNO3
(4biii) S + HNO3 ---> H2SO4(aq) + H2O(l) + 6NO2(aq)Aluminum does not react with conc.HNO3 due to the formation of protective coating of oxide on the metal.(4c)Al2O3 Aluminium oxide.
(3a)(i)all elements are made up of small indivisible particles called atoms(ii)atoms can neither be create nordestoryed (iii)when atoms combine with other atoms they do so in simple ratios(3aii)law of multiple proportion state when twoor more elements/compounds havemultiple ways of combining into different compounds.
.(3bi)-margarine-soap-candles(3bii) CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH + 2H2(g) ---------> CH3(CH2)6COOHCH3(CH2)14COOC2H5 + NAOH------->CH3(CH2)14COONa + C2H5OH(2ai)(i)dilute acids and metal (soluble salt)(ii)Alkali and acid (soluble salt)(iii)double decomposition
(2aii)(i)dilute acids and metal (soluble salt):Zn(s) + 2HCl(aq)--------->ZnCl(aq) + H2(aq)(ii)Alkali and acid (soluble salt): NaOH(aq)+HNO3(aq)----->NaNO3(aq)+H2O(s)(iii)double decomposition:AgNO3(aq)+NaCl(aq)------>AgCl(s)+NaNO3(aq)(2aiii)(i)used in manufacturing of glass(ii)used to standardized acid in the laboratory
(2b)The impure copper is made the anode inan electrolytic cell containing pure copperand cathodes and copper (II) tetra oxo-sulphate VI solutions as the electrolyteAt cathode4OH^(aq)---->2H2O(s) + (aq) + 4eAt anodeCu(s)----->Cu^2+(aq)+2e(2c)for sodium chloride = 39.0-36.6/39.0*100%=2.7/39*100%=0.0692*100%=6.92%for siliver nitrate = 952-297/952*100%=655/952*100%=68.8%
(1a)Helium' ^4 He has a stable electron con figuration compound Be because it hasa complete filled valance electron
(1bi)- After forming an ionic bond.1H becomes H^+ : it will have zero electron- After forming an ionic bond.3Li^+ becomes 3Li^+ : it will have two electrons.
1bii)- 1H^+ had one electron while neutral.On forming an ionic bond, it loses one electron- 3Li^+ had 3 electrons while neutral. On forming an ionic bond, it loses one electron
(1ci)Raw materials should be easily and cheaply obtainable
(1cii)Means of transport(1d)(i)low evolution of heat(ii)low energy waste.
(1e)No of moles of chlorine reacting = 21.3/71= 0.3molesFrom the equation, ratio at temperature to chlorine is 1:8No of moles of temperature = 0.3/8 = 0.0375Using the no. of moles = mass/molar mass mass of turpentine = 0.0375 x 136 = 5.1g
(1f)Cracking means breaking down ordecomposition of compound by the action of the heat alone
(1g)(i)stability(ii)size of atomic ratio(1h)Carbohydrates are naturally occurring organic compound containing hydrogen and oxygen with the hydrogen and oxygen present in the ratio of 2:1(1i)(i)A simple sugar is crystalline, starch is not(ii)A simple sugar is soluble in water ,starch is not(1j)(i)H2CO2/ H2CO3----->2H^+CO3^2-(ii)CH2COOH/CH2COOH----->CH2COO^1
waec-gce-2019-commerce
The
SUBJECT IS: Waec Gce Chemistry ANSWER'S
CHEMISTRY OBJ:
1-10: BDABADDCAA
11-20: DDBABDBBCC
21-30: -DA
waecgce-2019-literature-in-english
(4ai)Hardness of water is a situation where by water does not lather well with soap which is causes by dissolution of some salts like CaSO4 and MgSO4 in the water.
(4aiii)(i) It causes furging of kettles and boilers.
(ii) It causes waste of soap and water.
(4bi) Ammonia NH3, OxygenO2
(4bii) Ammonia is poured over heated platinum rhodium catalyst at 700°c to produce NO and steam which then in the presence of excess air gives NO2. It is then sprayed with hot water to formHNO3
(4biii) S + HNO3 ---> H2SO4(aq) + H2O(l) + 6NO2(aq)Aluminum does not react with conc.HNO3 due to the formation of protective coating of oxide on the metal.(4c)Al2O3 Aluminium oxide.
(3a)(i)all elements are made up of small indivisible particles called atoms(ii)atoms can neither be create nordestoryed (iii)when atoms combine with other atoms they do so in simple ratios(3aii)law of multiple proportion state when twoor more elements/compounds havemultiple ways of combining into different compounds.
.(3bi)-margarine-soap-candles(3bii) CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH + 2H2(g) ---------> CH3(CH2)6COOHCH3(CH2)14COOC2H5 + NAOH------->CH3(CH2)14COONa + C2H5OH(2ai)(i)dilute acids and metal (soluble salt)(ii)Alkali and acid (soluble salt)(iii)double decomposition
(2aii)(i)dilute acids and metal (soluble salt):Zn(s) + 2HCl(aq)--------->ZnCl(aq) + H2(aq)(ii)Alkali and acid (soluble salt): NaOH(aq)+HNO3(aq)----->NaNO3(aq)+H2O(s)(iii)double decomposition:AgNO3(aq)+NaCl(aq)------>AgCl(s)+NaNO3(aq)(2aiii)(i)used in manufacturing of glass(ii)used to standardized acid in the laboratory
(2b)The impure copper is made the anode inan electrolytic cell containing pure copperand cathodes and copper (II) tetra oxo-sulphate VI solutions as the electrolyteAt cathode4OH^(aq)---->2H2O(s) + (aq) + 4eAt anodeCu(s)----->Cu^2+(aq)+2e(2c)for sodium chloride = 39.0-36.6/39.0*100%=2.7/39*100%=0.0692*100%=6.92%for siliver nitrate = 952-297/952*100%=655/952*100%=68.8%
(1a)Helium' ^4 He has a stable electron con figuration compound Be because it hasa complete filled valance electron
(1bi)- After forming an ionic bond.1H becomes H^+ : it will have zero electron- After forming an ionic bond.3Li^+ becomes 3Li^+ : it will have two electrons.
1bii)- 1H^+ had one electron while neutral.On forming an ionic bond, it loses one electron- 3Li^+ had 3 electrons while neutral. On forming an ionic bond, it loses one electron
(1ci)Raw materials should be easily and cheaply obtainable
(1cii)Means of transport(1d)(i)low evolution of heat(ii)low energy waste.
(1e)No of moles of chlorine reacting = 21.3/71= 0.3molesFrom the equation, ratio at temperature to chlorine is 1:8No of moles of temperature = 0.3/8 = 0.0375Using the no. of moles = mass/molar mass mass of turpentine = 0.0375 x 136 = 5.1g
(1f)Cracking means breaking down ordecomposition of compound by the action of the heat alone
(1g)(i)stability(ii)size of atomic ratio(1h)Carbohydrates are naturally occurring organic compound containing hydrogen and oxygen with the hydrogen and oxygen present in the ratio of 2:1(1i)(i)A simple sugar is crystalline, starch is not(ii)A simple sugar is soluble in water ,starch is not(1j)(i)H2CO2/ H2CO3----->2H^+CO3^2-(ii)CH2COOH/CH2COOH----->CH2COO^1
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