National 5 (Scotland) · National 5 Chemistry

Chemical Changes and Structure

22 practice questions, each with the answer and an explanation.

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Random questions from this topic, one at a time. You see the answer and the explanation straight after each one.

All 22 questions

  1. An atom of sodium has atomic number 11 and mass number 23. How many protons, neutrons and electrons does it have?
  2. What are isotopes?
  3. What is the electron arrangement of a chlorine atom (atomic number 17)?
  4. The Group 1 metals become more reactive going down the group. What is the main reason?
  5. Sodium chloride does not conduct electricity when solid but conducts when molten. What is the reason?
  6. Which statement describes covalent bonding?
  7. Diamond is very hard and has a very high melting point. Why?
  8. Why can metals conduct electricity?
  9. What is the formula of aluminium oxide, given that aluminium forms Al³⁺ ions and oxygen forms O²⁻ ions?
  10. In the equation __Mg + O₂ → __MgO, what is the correct balancing number in front of MgO?
  11. What is the gram formula mass of calcium carbonate, CaCO₃? (Ca = 40, C = 12, O = 16)
  12. How many moles are there in 50 g of calcium carbonate (GFM 100)?
  13. What mass of sodium hydroxide (GFM 40) is in 0.25 mol?
  14. 0.5 mol of a solute is dissolved in 250 cm³ of solution. What is the concentration?
  15. How many moles of solute are in 200 cm³ of a 0.1 mol/l solution?
  16. 2Mg + O₂ → 2MgO. What mass of magnesium oxide (GFM 40) forms when 12 g of magnesium (GFM 24) burns completely in excess oxygen?
  17. CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂. What mass of carbon dioxide (GFM 44) is made when 10 g of calcium carbonate (GFM 100) reacts completely?
  18. In a titration 25.0 cm³ of hydrochloric acid is neutralised by 20.0 cm³ of 0.100 mol/l sodium hydroxide (HCl + NaOH → NaCl + H₂O). What is the concentration of the acid?
  19. Chlorine consists of 75% chlorine-35 and 25% chlorine-37. What is the relative atomic mass of chlorine?
  20. Propane burns in oxygen: C₃H₈ + __O₂ → 3CO₂ + 4H₂O. What number goes in front of O₂?
  21. 2H₂ + O₂ → 2H₂O. What mass of water (GFM 18) is made from 4 g of hydrogen (GFM 2)?
  22. What mass of carbon dioxide (GFM 44) is produced when 22 g of propane (GFM 44) burns completely: C₃H₈ + 5O₂ → 3CO₂ + 4H₂O?

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