VERIFIED NABTEB chemistry ANSWERS

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1.(iii)
Molar mass of YOH = conc. Of YOH solution mgdm^-3/conc. Of YOH solution in moldm-3
= 7.00/0.126145 = 55.5
YOH = 56, Y + 17 = 56
Y = 56-17
Y=39

(IV)
The element Y is potassium

(c)
i. Do not use more than 3 drop of indicator
ii. Use a white tile
iii. Shake the conical flask thoroughly during the titration
iv. Avoid running in the acid at a very fast rate


2a.
Observation
I. D dissolved completely in water to give a colorless solution
ii. Release of a colorless gas which turns lime water milky
iii. Dissolved in water to give brownish solution which turn red litmus paper blue
iv. Green solution obtained

v. Double decomposition reaction
bi.
X = Ammonia ( NH3)
Y = Ammonium chloride (NHiCl)
Z = Nitrogen (N) oxide (No2)

C.
i. Pb(No3)2(aq) + H2^3(g) ===> pbs + H20 + NO2
Black colour of pbs obtained and release of No2
ii. K2CrO7 + SO2 + H2SO4 ===> K2SO4 + cr2(SO4)3 + H20
SO2 changes orange color of k2cr207 solution to a clear green solution cr2(so4)


3ai.
I --- delivery tube
II --- combustion tube
III --- beaker
IV --- collecting tube

(ii)
W is hydrogen gas
(iii)
The gas W gives a pop sound with lighted splinter
(Iv)
CUO + H2 ---> CU + H20
(1) from black to blue
(2) formation of water obtained

bi.
Downward delivery I.e upward displaced cement by air
(ii) I. Decolourisation (from purple to colorless)
ii. Reddish - brown ppt obtained

C. Tabulate
Test = glucose + Fehling solution + boiling
Observation = A yellow ppt obtained



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