EmSAT Achieve (UAE) · Chemistry

Matter, Atomic Structure and Chemical Bonding

26 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 26 questions

  1. What is the complete ground-state electron configuration of a neutral iron atom (atomic number Z = 26)?
  2. Which of the following elements has the highest first ionization energy?
  3. According to VSEPR theory, what is the molecular geometry of sulfur tetrafluoride (SF₄)?
  4. What mass of anhydrous sodium carbonate (Na₂CO₃, molar mass = 106 g/mol) is required to prepare 250 mL of a 0.20 M aqueous solution?
  5. Which intermolecular force is primarily responsible for the unusually high boiling point of water compared to hydrogen sulfide (H₂S)?
  6. A compound consists of 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is its empirical formula? (Atomic masses: C = 12.0, H = 1.0, O = 16.0)
  7. Which set of quantum numbers (n, l, m_l, m_s) represents a valid electron in an orbital?
  8. What is the total number of valence electrons present in the nitrate polyatomic anion (NO₃⁻)?
  9. Which of the following bonds exhibits the greatest ionic character based on Pauling electronegativity differences?
  10. What is the hybridization of the central carbon atom in ethyne (acetylene, C₂H₂)?
  11. Which statement correctly describes the trend in atomic radius across Period 3 of the periodic table from sodium to chlorine?
  12. In a mass spectrometer, a sample of neon exhibits two major isotopic peaks: ²⁰Ne (abundance 90.5%) and ²²Ne (abundance 9.5%). What is the relative atomic mass of neon?
  13. How many sigma (σ) and pi (π) bonds are present in a single molecule of propene (CH₃–CH=CH₂)?
  14. What volume of oxygen gas at STP is produced by the complete thermal decomposition of 0.20 moles of potassium chlorate according to 2KClO₃(s) → 2KCl(s) + 3O₂(g)?
  15. Which of the following molecules has a permanent net dipole moment (is polar)?
  16. What is the formal charge on the central oxygen atom in an ozone molecule (O₃), where the Lewis structure shows one O=O double bond and one O–O single bond with a complete octet?
  17. Which gaseous sample contains the greatest total number of atoms under identical temperature and pressure conditions?
  18. Which element has the electron configuration [Kr] 5s² 4d¹⁰ 5p³?
  19. According to the kinetic molecular theory of gases, what happens to the average kinetic energy of gas molecules when absolute temperature is doubled?
  20. Which crystalline solid type is characterized by high melting point, electrical conductivity in the molten state, and brittleness in the solid phase?
  21. What is the oxidation number of chromium in the dichromate ion (Cr₂O₇²⁻)?
  22. Which gas deviates most significantly from ideal behavior under high pressures and low temperatures?
  23. What is the mass percent of nitrogen in ammonium nitrate (NH₄NO₃, molar mass = 80.0 g/mol)? (Atomic mass N = 14.0 g/mol)
  24. Which orbital transition in a hydrogen atom emits a photon with the shortest wavelength?
  25. What is the empirical formula of a hydrocarbon that contains 85.7% carbon and 14.3% hydrogen by mass?
  26. Which of the following molecules has a linear molecular geometry?

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