NOTE THAT ^ MEANS RAISE TO POWER.
* MEANS MULTIPLY.
TABULATE MEANS TO DRAW A TABLE.
(1a) volume of pipette=25.00cm3
Indicator = methyl orange
(1a11)
TABULATE:
Burrette Reading(cm3)|Rough|1st |2nd |3rd |
Final reading: |23.01|24.00|24.01|24.00|
Initial reading:|0.00|0.00 |0.00 |0.00|
Volume of acid used: |23.01|24.00|24.01|24.00|
Average volume of acid=(24.00+24.01+24.00)/3
= 72.01cm3/3 =24.00cm3
(1bii) conc. of B in moldm^-3
CAVA/CBVB =nA/Nb
where
CA=0.053
CB =?
VB =25.00
VA =24.00
NA =1
NB = 2
CB = CAVA*NB/VB*NA
=0.053*24.00*2/25.00*1
=2.544/25.00= 0.101moldm^-3
(1biii) 1dm^3 of 0.101moldm-^ KOH = X
X = 0.101*6.00*10^23
X = 0.606*10^23.
(1aiii) H2504(aq)+2KOH(aq)-->K2504(aq)+2H20(l)
(1bi) conc .of A in moldm-3
molarity=concentration in gdm-3/Molar mass
...conc.in gldm3=A has 1.30g
H2S04 in 250cm3
Xg = 1000cm3
X =1.30*1000/250
Xg = 5.2g/dm^3
Molar mass of H2S04=
2*1+32.0+ (16*4)
= 2+32.0+64
= 98gmol^-1
Conc.in moldm^-3 =conc. (gdm^-3)
= 5.2/98 =0.053moldm^-1
(2ai)TEST:
Sample C + water + litmus paper
OBSERVATION:sample c soluble in water to give a colourless solution, turn red litmus paper blue
INFERENCE: basic solution
(2aii)
TEST:solution from (ai) +Ba(No3)2+ dilute HN03 acid in excess
OBSERVATION:White ppt/ prcipetate formed.ppt dissolved forming a colourless solution, colourless gas with irritating smell evolved, the gas turned the colour of acidified K2CR207 solution from orange to green
INFERENCE: SO3^2-, S04^2- or
CO2^3- or S^2- suspected/present. the gas is S02 FROM SO4^2-
(2aiii)
TEST: solution from (ai) + NaOH(aq) solution + warm gently.
OBSERVATION: colourless gas evolved with characterisics choking smell turns litmus blue and from white fumes with conc./ stopper vapour.
INFERENCE: Gas is NH3,NH4^+ present.
(2bi)
TEST:sample D + distilled water + boil
OBSERVATION: partially/sparingly soluble in water, white residue colourless filtrate
(2bii)
TEST: solution from (bi) + iodine solution
OBSERVATION: blue-black ppt formed
INFERENCE: Starch is present
(2biii)
TEST:solution from (bi) fehling's solution + warm
OBSERVATION:no visible reaction
INFERENCE: Starch is non reducing sugar (glucose)
(2biv)
OBSERVATION: solution from b(i) + dilute HCL + boil + fehling's solution on hot.
TEST: brick red ppt formed
INFEREENCE:starch has been hydrolysed to reducing sugar. (glucose)
(3ai) sublimation
(3aii) fractional distillation
(3bi)
On heating pb (NO3)2, THE CRYSTAL BREAk UP WITH THE CHARACTERISTICS CRACKLING SOUND. MELTING OCCURS AND A BROWN GAS, NITROGEN
(IV)OXIDE, MIXED WITH OXYGEN IS GIVEN OFF.
2pb (N03)2----->2pbO(S) + 4NO2(g) + O2(g)
(3bii)
it decolourises from orange to orange.
Title : Nabteb Chemistry Practical Questions And Answers Now Available
Description : NOTE THAT ^ MEANS RAISE TO POWER. * MEANS MULTIPLY. TABULATE MEANS TO DRAW A TABLE. (1a) volume of pipette=25.00cm3 Indicator = methyl ...
