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NECO SSCE Chemistry 2019 past questions and answers

This 2019 NECO SSCE Chemistry set has 40 practice questions. Try these 5 free sample questions, tap a question to reveal the answer and explanation. Then practise the whole 2019 set with instant marking.

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Sample NECO SSCE Chemistry 2019 questions

1. A compound contains 6.0 g of carbon and 16.0 g of oxygen. What is the simplest mole ratio of carbon to oxygen? (C = 12, O = 16)
  1. 1:2
  2. 1:1
  3. 2:1
  4. 2:3

Answer: A. 1:2

The amounts are 6.0/12 = 0.50 mol C and 16.0/16 = 1.00 mol O, giving the simplest ratio 1:2.

2. Which equation correctly represents the reaction of magnesium with oxygen to form magnesium oxide?
  1. Mg + O2 -> MgO
  2. 2Mg + O2 -> 2MgO
  3. Mg + 2O2 -> MgO2
  4. 2Mg + 2O2 -> 2MgO

Answer: B. 2Mg + O2 -> 2MgO

Two magnesium atoms combine with one oxygen molecule to give two formula units of magnesium oxide.

3. At room temperature and pressure, 1 mol of a gas occupies 24 dm3. What volume is occupied by 0.50 mol of the gas under the same conditions?
  1. 6 dm3
  2. 10 dm3
  3. 12 dm3
  4. 48 dm3

Answer: C. 12 dm3

The volume is 0.50 x 24 = 12 dm3.

4. A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass. What is its empirical formula? (C = 12, H = 1, O = 16)
  1. C2H4O2
  2. CH4O
  3. C2H2O
  4. CH2O

Answer: D. CH2O

For 100 g, the mole amounts are about 3.33 C, 6.7 H and 3.33 O, which reduce to 1:2:1.

5. An ion has 17 protons, 18 neutrons and 18 electrons. Which description is correct?
  1. A neutral chlorine-35 atom
  2. A chloride-35 ion with a -1 charge
  3. A chloride-36 ion with a -1 charge
  4. An argon-35 ion with a +1 charge

Answer: B. A chloride-35 ion with a -1 charge

Seventeen protons identify chlorine, the mass number is 17 + 18 = 35, and one extra electron gives a -1 charge.

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