CHE1503
ASSESSMENT 1
2025
, QUESTION 1
SOLUTION:
Title: Determination of percentage of BaCl2 ∙ 2H2 O in an unknown sample
Aim: To determine the percentage of BaCl2 ∙ 2H2 O in an unknown sample by heating and measuring
the mass loss as a result of dehydration.
Flow diagram:
Obtain hot plate and heat for 5 minutes at 300°C
Place clean, dry evaporating dish on
the hot plate for 5 minutes
Remove dish (with tongs) and cool for 10 minutes on wire mesh
Weigh cooled evaporating dish
Add 1.5 g of sample and record total weight
Heat the sample on the hot plate for 15 minutes
Remove dish, place on wire mesh, and cool for 10 minutes
Weight the dish + residue
Reheat for 15 minutes, then cool for 10 minutes, and reweigh
Calculate weight loss to determine percentage of
sample
, QUESTION 2
SOLUTION:
a).
Chemical equation (eq 3):
CaC2 O4 ∙ H2 O ⃗⃗⃗⃗⃗⃗⃗⃗⃗⃗⃗⃗
200℃ CaC2 O4 + H2 O
i).
Mass of crucible + cover = 28.120 g
Mass of covered crucible + sample = 31.020 g
Mass of covered crucible + sample after heating = 30.141 g
mass(CaC2 O4 ∙ H2 O) = (Mass of covered crucible + sample) − (Mass of crucible + cover)
= 31.020 − 28.120
= 2.900 g
mass(H2 O) = (Mass of covered crucible + sample after heating) − (Mass of covered crucible + sample)
mass(H2 O) = 31.020 − 30.141
= 0.879 g
ASSESSMENT 1
2025
, QUESTION 1
SOLUTION:
Title: Determination of percentage of BaCl2 ∙ 2H2 O in an unknown sample
Aim: To determine the percentage of BaCl2 ∙ 2H2 O in an unknown sample by heating and measuring
the mass loss as a result of dehydration.
Flow diagram:
Obtain hot plate and heat for 5 minutes at 300°C
Place clean, dry evaporating dish on
the hot plate for 5 minutes
Remove dish (with tongs) and cool for 10 minutes on wire mesh
Weigh cooled evaporating dish
Add 1.5 g of sample and record total weight
Heat the sample on the hot plate for 15 minutes
Remove dish, place on wire mesh, and cool for 10 minutes
Weight the dish + residue
Reheat for 15 minutes, then cool for 10 minutes, and reweigh
Calculate weight loss to determine percentage of
sample
, QUESTION 2
SOLUTION:
a).
Chemical equation (eq 3):
CaC2 O4 ∙ H2 O ⃗⃗⃗⃗⃗⃗⃗⃗⃗⃗⃗⃗
200℃ CaC2 O4 + H2 O
i).
Mass of crucible + cover = 28.120 g
Mass of covered crucible + sample = 31.020 g
Mass of covered crucible + sample after heating = 30.141 g
mass(CaC2 O4 ∙ H2 O) = (Mass of covered crucible + sample) − (Mass of crucible + cover)
= 31.020 − 28.120
= 2.900 g
mass(H2 O) = (Mass of covered crucible + sample after heating) − (Mass of covered crucible + sample)
mass(H2 O) = 31.020 − 30.141
= 0.879 g
