NECO Chemistry Past Questions And Answers (Objective and Theory)
Section A (Objective)
Question: What is the chemical formula for hydrochloric acid?
A) HCl
B) H₂SO₄
C) NaOH
D) CH₄
Answer: A) HCl
Question: Which gas is responsible for the characteristic odor of rotten eggs?
A) Hydrogen sulfide (H₂S)
B) Methane (CH₄)
C) Nitrous oxide (N₂O)
D) Sulfur dioxide (SO₂)
Answer: A) Hydrogen sulfide (H₂S)
Question: What is the molar mass of carbon dioxide (CO₂)?
A) 12 g/mol
B) 16 g/mol
C) 28 g/mol
D) 44 g/mol
Answer: D) 44 g/mol
Question: In the periodic table, which group do halogens belong to?
A) Group 1
B) Group 7
C) Group 14
D) Group 18
Answer: B) Group 7
Question: What is the product of the complete combustion of hydrocarbons in sufficient oxygen?
A) Carbon monoxide (CO)
B) Water (H₂O)
C) Nitrogen oxides (NOx)
D) Sulfur dioxide (SO₂)
Answer: B) Water (H₂O)
Section B (Theory) – Continued
Question: Explain the concept of stoichiometry in chemical reactions, illustrating its application with an example.
Answer: Stoichiometry involves the quantitative relationships in chemical reactions. For example, in the reaction 2H₂ + O₂ → 2H₂O, stoichiometry shows that two moles of hydrogen react with one mole of oxygen to produce two moles of water.
Question: Discuss the principles behind the titration technique in analytical chemistry, emphasizing its importance and applications.
Answer: Titration is a technique to determine the concentration of a solution by reacting it with a solution of known concentration. It’s crucial in analytical chemistry for accurate measurements in areas like pharmaceuticals and environmental monitoring.
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Section A (Objective) – Continued
Question: Which of the following is a non-metal?
A) Sodium
B) Bromine
C) Calcium
D) Magnesium
Answer: B) Bromine
Question: What is the chemical formula for ammonia?
A) NH₄
B) N₂H₄
C) NH₃
D) NO₃
Answer: C) NH₃
Question: In the electrolysis of water, which gas is collected at the cathode?
A) Hydrogen
B) Oxygen
C) Chlorine
D) Nitrogen
Answer: A) Hydrogen
Question: Identify the reducing agent in the reaction: 2Fe₂O₃ + 3C → 4Fe + 3CO₂.
A) C
B) Fe₂O₃
C) CO₂
D) Fe
Answer: A) C
Question: What is the empirical formula of a compound composed of 25% nitrogen and 75% oxygen by mass?
A) NO₂
B) N₂O₅
C) NO
D) N₂O
Answer: A) NO₂
Section B (Theory)
Question: Discuss the concept of ionization energy, explaining how it varies across the periodic table and its significance in chemical behavior.
Answer: Ionization energy is the energy required to remove an electron from an atom. It increases across a period and decreases down a group in the periodic table. It influences chemical reactivity and bonding tendencies.
Question: Describe the process of polymerization, providing examples of synthetic and natural polymers. Explain their importance in daily life.
Answer: Polymerization is the process of combining monomers to form polymers. Examples include nylon and DNA (synthetic) and proteins and cellulose (natural). Polymers have diverse applications, from clothing to medical devices.
