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NECO SSCE Chemistry 2018 past questions and answers

This 2018 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 2018 set with instant marking.

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Sample NECO SSCE Chemistry 2018 questions

1. An element has two isotopes, X-35 and X-37, with natural abundances of 75% and 25% respectively. What is its relative atomic mass?
  1. 36.0
  2. 35.0
  3. 35.5
  4. 37.0

Answer: C. 35.5

The weighted mean is (35 x 75 + 37 x 25)/100 = 35.5.

2. What generally happens to the atomic radius of elements as one moves from left to right across a period?
  1. It decreases
  2. It increases
  3. It remains exactly constant
  4. It first doubles and then halves

Answer: A. It decreases

Increasing nuclear charge across a period attracts the electron shells more strongly without adding a new shell.

3. Many simple covalent substances have low boiling points because their molecules are held together by
  1. strong metallic bonds
  2. strong ionic attractions
  3. covalent bonds between all molecules
  4. weak intermolecular forces

Answer: D. weak intermolecular forces

Boiling a simple molecular substance mainly overcomes weak attractions between molecules, not the covalent bonds within them.

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. CH2O
  3. CHO2
  4. CH4O

Answer: B. CH2O

For 100 g, the mole ratio is 40/12 : 6.7/1 : 53.3/16, which is approximately 1 : 2 : 1.

5. What mass of sodium carbonate, Na2CO3, is present in 0.25 mol? (Na = 23, C = 12, O = 16)
  1. 10.6 g
  2. 26.5 g
  3. 53.0 g
  4. 106.0 g

Answer: B. 26.5 g

The molar mass of Na2CO3 is 106 g mol-1, so 0.25 mol has a mass of 26.5 g.

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