Volume = 25.0 cm³ = 0.025 dm³
Moles = 0.100 × 0.025
= 0.0025 mol
Answer:
0.0025 mol
2026 NECO Practical Chemistry Questions and Answers
QUESTION 2 – Qualitative Analysis of Specimen C
Experiment
Add sodium hydroxide solution to specimen C.
Observation
Light blue precipitate formed.
Precipitate insoluble in excess NaOH.
Inference
Copper (II) ion present.
Cu²⁺
Additional Test
Add aqueous ammonia.
Observation
Light blue precipitate dissolves in excess ammonia to give deep blue solution.
Inference
Copper (II) ion confirmed.
Equation
Cu²⁺ + 2OH⁻ → Cu(OH)₂
QUESTION 3 – Qualitative Analysis of Specimen D
Procedure
Add sodium hydroxide solution.
Observation
Dirty green precipitate formed.
Turns brown on standing.
Inference
Iron (II) ion present.
Confirmation
Add aqueous ammonia.
Observation
Green precipitate formed.
Turns brown after exposure to air.
Inference
Fe²⁺ confirmed.
Equation
Fe²⁺ + 2OH⁻ → Fe(OH)₂
QUESTION 4 – Anion Test
Procedure
Add dilute nitric acid to specimen.
Add barium chloride solution.
Observation
White precipitate formed.
Precipitate insoluble in dilute nitric acid.
Inference
Sulphate ion present.
SO₄²⁻
Equation
Ba²⁺ + SO₄²⁻ → BaSO₄
QUESTION 5 – Gas Preparation and Identification
Procedure
Add dilute hydrochloric acid to marble chips.
Observation
Effervescence observed.
Gas evolved.
Test
Pass gas through lime water.
Observation
Lime water turns milky.
Inference
Carbon dioxide present.
Equation
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂
QUESTION 6 – Determination of Water of Crystallization
A hydrated salt has:
Mass of crucible = 20.00 g
Mass of crucible + hydrated salt = 24.50 g
Mass after heating = 23.60 g
Calculate:
(a) Mass of hydrated salt
24.50 − 20.00
= 4.50 g
(b) Mass of water lost
24.50 − 23.60
= 0.90 g
(c) Percentage water
Percentage water
= (0.90 ÷ 4.50) × 100
= 20%
Answer:
20%
2026 NECO Practical Chemistry Questions and Answers
QUESTION 7 – Solubility and Crystallization
Procedure
Heat saturated solution of potassium nitrate.
Allow to cool.
Observation
Crystals formed on cooling.
Explain why crystals formed.
Answer:
The solubility of potassium nitrate decreases as temperature decreases. Excess dissolved salt separates out as crystals when the solution cools.
State two conditions necessary for crystallization.
Answer:
- Saturated solution.
- Slow cooling.
QUESTION 8 – Practical Calculations (Advanced NECO Standard)
A student dissolved 5.30 g of sodium carbonate (Na₂CO₃) in water and made up the solution to 250 cm³.
Calculate:
(a) Molar mass of Na₂CO₃
Na = 23 × 2 = 46
C = 12
O = 16 × 3 = 48
Total = 106 g mol⁻¹
Answer:
106 g mol⁻¹
Moles = Mass ÷ Molar Mass
= 5.30 ÷ 106
= 0.05 mol
(c) Concentration of solution
Using molarity:
