NECO 2019 chemistry practical answers available 💯✔

NECO 2019 chemistry practical  answers available 💯✔

.
(1)
The volume or pipette used 25.00cm³

In a tabular form
Titrations |rough |1st|2nd|3rd|
Final reading |21.00|41.30|20.40|40.90
Initial reading|0.00|21.00|0.00|20.40
Vol of A used |21.00|20.30|20.40|20.50
.
(1ai)
Average volume of A = 20.30+20.40+20.50/3
=61.2/3
=20.40cm³
.
(1aii)
H2X(aq) + 2NaOH(aq)-->Na2X(aq) + 2H2O(l)
.
(1bi)
Mass conc. of B = 1g/250cm³
= 1g/0.25dm³ = 4g/dm³
Using :
Molar conc. = mass conc./molar mass
= 4/(23+16+1) = 4/40 = 0.1mol/dm³
.
(1bii)
Using CAVA/CBVB = nA/nB
CA = CBVBnA/VAnB
CA = 0.1×25×1/20.4×2
Concentration of A = 0.06127mol/dm³
.
(1biii)
Molar mass of A = mass conc/molar conc
=4.85/0.6127
=79.15
≅ 79gmol
.
(1c)
(i)it might contain traces of impurities which must be removed before being weighed
(ii)it is hygroscopic which readily absorb moisture from atmosphere
.
Sagirzakariyya2048@gmail.com