VERY IMPORTANT INFORMATION FOR NUMBER 1!!!
PLEASE REMEMBER TO USE YOUR'S SCHOOL'S AVERAGE TITRE VALUE(AVERAGE VOLUME OF ACID). WE USED 23.00cm3, TRY TO KNOW YOUR SCHOOL'S AVERAGE TITRE VALUE. ASK YOUR CHEMISTRY TEACHER. THEN, ANYWHERE YOU SEE 23.00cm3 IN MY CALCULATION, PUT YOUR SCHOOL'S OWN AND RE-CALCULATE. THIS IS VERY IMPORTANT!!!
Indicator used is methyl orange.
Volume of pipette used is 25cm³
Final burette reading cm³|23.50|23.00|23.00|33.00|
Initial burette reading cm³| 00|0.00|0.00|10.00|
Volume of acid used(cm³) |23.50|23.00|23.00|23.00|
Average volume of A used = 23.00+23.00+23.00/3 =23.00cm³
Equation for the reaction
Concentration of A in moldm³ =concentration in gldm³.
3.6g of A =500cm²
Xg of A will be = 10000³
Xg=3.65*1000/500 =36.5/5 =7.3gldm³
Molar Mass of A HCl=1+35.5=36.5
Concentration of A =7.3gldm³/36.5gldm³
Concentration of B in moldm³
concentration of A in moldm³ CA=0.20
Volume of used VA=23.00
Concentration of B in moldm³ CB=?
Volume of B used VB= 25.00
CAVA/CBVB = n(A)/n(B) =2/1
Molar mass of B in glmol
Concentration of B(moldm-³)= conc gldm³/molar mass
0.092 * molar mass =10.60gldm³
Molar mass =10.60gldm³/0.092
Relative atomic mass of X in X²CO³
No of moles of X2CO3 = molarity × volume
= 0.092 × 25
Mole ratio of X2CO3 to CO2 is 1:1
Therefore, No of moles of CO2 released = 2.3moles
Volume of CO2 released = 2.3 × 22.4
2022 NECO CHEMISTRY PRACTICAL Questions & Answers (ESSAY, OBJ, THEORY, PRACTICALS ETC)
TEST: C + 5cm³ of distilled water and shake thoroughly. Divide the solutions into three portions.
OBSERVATION: A pale green solution results
INFERENCE: Salt is soluble
TEST: To the first portion add NaOH solution in drys
OBSERVATION: Dark green gelatinous was formed
INFERENCE: Fe²+ present
TEST: then in excess
OBSERVATION: Precipitate is insoluble
INFERENCE: Fe²+ present
TEST: To the second portion add K3Fe(CN)6 solution
OBSERVATION: A dark blue precipitate formed
INFERENCE: Fe²+ confirmed
TEST: To the third portion add AgNO³ solution
OBSERVATION: White Precipitate formed
INFERENCE: SO4²- , CL- CO²- present
TEST: To the results obtained in add dilute HNO3 in drops , then excess
OBSERVATION: White Precipitate is insoluble
INFERENCE: CL- present
TEST: To the results obtained in add NH3 solution
OBSERVATION: White Precipitate dissolves
INFERENCE: CL- Confirmed
You can subscribe now to enjoy early subscription benefits..
2021 EXAM DATES
NECO: 5th July - 16th August
WAEC: 16th August - 30th Sept
Answers to be sent midnight or a day before exam.
Note: There is nothing like JAMB Score upgrading and we don't do it. Please disregard anyone impersonating us trying to scam you with JAMB Score Upgrading.