Weac 2017/2018 WASSCE May/June Physics/Agricultural/Chemistry/Biology Practical Specimens Questions And Answers solutions
Tabulate
Burette reading|Final burette reading
(cm^3)|Initial burette reading (cm^3)|
Volume Naijacomms.com of acid used(cm^3)|
Rough- 24.10,0.00,24.10
First- 23.80, 0.00, 23.80
Second- 23.75, 0.00, 23.70
Third- 23.75, 0.00, 23.75
Average volume of A used = 23.80 + 23.70 + 23.75cm^3/3
=23.75cm^3
1bi)
CAVA/CcVc=2/1
Cc=CAVA/2VC naijacomms.com
=0.100*23.75Moldm^-3/2*25.00
=0.0475moldm^-3
amount of A used = 0.100x VA/1000=0.100*23.75/1000 =0.00237
2moles Of A = 1mole of C
0.002375mol of A = 0.002375mol/2
100cm^3 of C contain 0.00237*100mol/2*25 =0
1000cm3ofCcontained0.002375x1000mol
2x25
=0.0475mol
concentration of C in moldm-3 =0.0475moldm-3
1bii)
Molar mass of Bing mol-1:
Molar mass of Na2CO3.yH2O=mass concentration of Bingdm-3
molar concentration of Binmoldm-3
=13.6gdm-3
0.0475moldm-3
=286gmol-1
1biii)
Molar mass of Na2CO3 =[(2×23)+12+(16×3)]=106gmol-1
Mass of anhydrous Na2CO3=106x0.0475gdm-3
=5.035gdm-3
Mass of water=13.6-5.035gdm-3
=8.565gdm-3
Mass of Na2CO3 =Molar mass of Na2CO3
Mass naijacomms.com for all waec 2017 answers of water y×Molar mass of water
5.035=106
8.565 18y
y =106x8.565
5.035x18
=10
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(2)Tabulate
Test
(a)(i)Fn+H2O,then
filter
Observation
White residue and blue
filtrate was observed
Inference
Fn is a mixture of
soluble and insoluble
salts
Test
(ii)Filtrate+NaOH(aq)in
drops,then in excess
Observation Naijacomms.com
A blue gelatinous
precipitate which is
insoluble in excess
NaOH(aq)was formed
Inference
Cu2+present
Test
(iii)Filtrate+NH3(aq)in
drops,then in excess
Observation
A pale blue gelatinous
precipitate was
formed. The precipitate
dissolves or is soluble
in excess NH3(aq)to give
a deep blue solution
Inference
Cu2+confirmed
Test
(iv)Filtrate+dil.HNO3
+AgNO3(aq)
Observation
Naijacomms.com
No visible reaction
White precipitate
formed
Inference
Cl-present
Test
+NH3(aq)in excess
Observation
Precipitatedissolvedin
excessNH3(aq)
Inference
Cl-confirmes
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PHYSICS SPECIMENS
2017 PHYSICS PRE_EXAMINATION. PRACTICAL ANALYSIS.
QUESTION3:
APPARATUS :you are provided with cells, a potentiometre, an ammeter, a batteries, volt Meyer, a bulb, a key and jockey, naijacomms.com for answers and other necessary materials
a) Draw the Diagram.
i) measure and records the E. M. F. of the battery.
ii) set -up a circuit as show in the diagram above
iii) close the key K and use jockey to make a firm contact at J on the potentiometer wire such that P J=x =10cm.
iv) take and record the volt meter reading and corresponding value on the ammeter.
v) repeat the procedure for other values of x=20,30,40,50,and 60cm.
vi) Evaluate log V and log I.
vii) Tabulate your readings.
viii) plot a graph of log I on the vertical axis and log lolthe horizontal axis.
ix) Determine the slop s, of the graph.
x) Determine the intercept C, on the vertical axis.
xi) State the precautions taken to ensure accurate result.
bi) How is the brightness the bulb affected as X increases and a reason.
bii) List two electrical devices whose action do not support or obey ohm's law.
QUESTION 2:
Aim :Effect of dissolved substances on the boiling point of water.
Apparatus :Beaker (0-500cm3),water (distiller) measuringfree waec answers at naijacomms.com cylinder (6x) Thermometer (0-200 degree centigrade), stirrer tripod stand with guard stop watch /clock, Table salt (10g x5)
Draw the diagram. Procedure :
i) fill the beaker half -full with (200cm 3)water heat steadily until it boils for 3min
ii) Record the temperature of the boiling water ,Bo.
iii) And log of the common salt and stir to form a solution while visit naijacomms.com heating until another boiling point Bi is attained.
iv) Read and record Bi.
v) Evaluate x=Bi-Bo .
vi) Use the same mixture repeat the procedure four more times by adding of salt each time to give cumulative mass M of salt 20,30,40,and 50.
vii) In each case allow the mixture to boil steadily for at least 2min, then read and record the boiling point Bi.
viii) Tabulate your readings.
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ix) Plot a graph of Mi on the vertical axis and X on the horizontal axis.
x) Determine the slop of the graph.
xi) State two precautions taking to ensure accurate readings......revisit this page after 2minutes for answers to appear
= restort stand with clamp
= cork
= single grooved pulley of about 8cm radius with hole in its centre [remove all accessories on the pulley]
= Optical pins, weight hanger
= Slotted masses [ 50g, 70g, 110g, 130g ]
= thread
= about 3m
= stop watch
= tissue paper/pad
= meter rule
= measuring rape
Question 2
= equilateral triangular glass prism
= Four optical pins
= Four thumb pins
= Cellatex board
= drawing papers
Question 3
= Resistance box capable of reading 1m to 10m
= Voltmeter (0.5v)
= Plug key
= Two dry cells each of emf (1.5v)
= six connecting wires.
AGRICULTURAL SPECIMENS
======================
Specimen A: Born
Specimen B: Horn
Specimen C: Hoof
Specimen D: water (labelled)
Specimen E: Cowpea seeds
Specimen F: Tridax
Specimen G: Goat Weed
Specimen H: sida
Specimen I: Spear grass
Specimen J: Elephant grass
Specimen K: Pig weed
Specimen L: Water leaf
Specimen M: Urea (labelled)
Specimen N: Compost manure (labelled)
CHEMISTRY SPECIMENS
====================
== diluted Sodium hydroxide solution
== diluted ammonia solution
== diluted hydrochloric acid
== distilled water
== red and blue litmus paper fehlings solution (III)
Concentrated tetraoxosulphate (VI) solution (H2SO4)
== freshly prepared iron (II) tetraoxosulphate (VI) solution (Fe2SO4)
== burette (50cm3) ,filtration apparatus-- methyl orange
== boiling tube, test tube
== SALTS;.CuO, ZnSO4, Na2CO3.
BIOLOGY SPECIMENS
==================
Group I
Specimen A: twig of mango plant
Specimen B: twig of ixora plant
Specimen C: leaf of Hibiscus plant
Specimen D: hibiscus flower
Specimen E: green vegetable cut beef
Specimen F: a piece of freely cut beef
Specimen G: worker bee (wet preserved)
Specimen H: soldier termite (wet preserved)
Specimen J: adult cockroach (wet preserved)
Specimen K: nymph of cockroach (wet preserved)
Specimen M: quill feather
Specimen B: scale of bony fish
Specimen P: freshly preserved mammalian skin preferably of goat or ram with hair/fur.
Measuring at least 4cm by 4cm placed in a petric dish.
Group II
Specimen Q: slide of Hydra
Specimen R: small mammal (rat/rabbit/Guinea pig), wet preserved
Group III
Specimen S: a small amount of garden soil in a petric dish.
Specimen T: Orange/lemon/lime/citrus fruits.
Specimen V: tomato fruit
Specimen W: cassava tuber
Specimen XI: stem of young cassava plant measuring at 10cm in length.
Specimen XII: stem of young cassava plant measuring at least 10cm in length as in (XI)
NB: (i) specimens Q and R are peculiar to candidates in Ghana only and should not be provided to candidates in Nigeria, Sierra Leone and Gambia.
(ii) specimens S,T,V,W,XI,XII are peculiar to candidates in Nigeria, Sierra Leone and Gambia only and should not be provided to candidates in Ghana.
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