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Past Questions and Answers

NECO Chemistry Past Questions And Answers (Objective and Theory)

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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


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


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.

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