Try 10 free Chemistry questions below, each with the answer explained. When you are ready, practise all 866 on a timed CBT screen.
The NECO SSCE (June/July) is the National Examinations Council's final exam for Nigerian secondary school students. Like WAEC, each subject has an objective paper and a theory paper, and the syllabus covers the same topics.
Tap an answer to check it and see the explanation.
How many molecules are in 0.25 mol of carbon(IV) oxide? (Avogadro's constant = 6.02 × 10²³ mol⁻¹)
Answer: A. Number of particles = moles × Avogadro's constant = 0.25 × 6.02 × 10²³ = 1.505 × 10²³.
A gas occupies 66 cm³ at 27 °C. Find its volume at 77 °C, pressure remaining constant.
Answer: C. Charles's law uses kelvin: 27 °C = 300 K and 77 °C = 350 K. V₂ = 66 × 350 ÷ 300 = 77 cm³.
Express 0.5 mol/dm³ HNO₃ solution in g/dm³. (H = 1, N = 14, O = 16)
Answer: C. Mass concentration = molar concentration × molar mass = 0.5 × 63 = 31.5 g/dm³.
A current of 5 A flows for 11 minutes. Find the quantity of electricity passed.
Answer: B. Q = It = 5 × (11 × 60) = 3,300 C (time must be in seconds).
What is the pH of 0.00001 mol/dm³ nitric acid? (Assume it ionises completely.)
Answer: A. [H⁺] = 0.00001 = 10⁻⁵ mol/dm³, and pH = −log[H⁺] = 5.
Calculate the percentage by mass of nitrogen in NH₃. (N = 14, H = 1)
Answer: D. % of nitrogen = (mass of nitrogen in one formula unit ÷ molar mass) × 100 = 82.4%.
A test for hydrogen chloride is that the gas
Answer: C. Hydrogen chloride forms dense white fumes with ammonia.
What is the functional group of alkanones?
Answer: C. The functional group of alkanones is C=O within the chain (ketone).
What is the atomic number of carbon?
Answer: B. Carbon has 6 protons, so its atomic number is 6.
Which of these is a noble gas?
Answer: C. Argon is in Group 0 (Group 18), the noble gases.
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Create a free accountQuestions in the MyGradePrep bank for each topic.
| Topic | Questions |
|---|---|
| Mole concept | 226 |
| Gas laws | 120 |
| Periodic table | 69 |
| Solutions | 67 |
| Atomic structure | 61 |
| States of matter | 61 |
| Electrolysis | 61 |
| Solubility | 60 |
| Chemical formulae | 40 |
| Organic chemistry | 38 |
| Acids, bases and salts | 18 |
| Redox | 18 |
| Gases | 14 |
| Separation techniques | 10 |