Chemistry SL
Structure 1: models of particulate nature of matter — Structure 1
- 1.
State the three states of matter, and describe the arrangement and movement of particles in each.
[3 marks] · no calculator - 2.
Marking analysis: A learner attempts the following task: “State the three states of matter, and describe the arrangement and movement of particles in each.” Their response addresses only this point: “States solid, liquid and gas as the three states of matter.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 3.
An atom of chlorine-35 has atomic number 17. State the number of protons, neutrons and electrons it contains.
[3 marks] · no calculator - 4.
Marking analysis: A learner attempts the following task: “An atom of chlorine-35 has atomic number 17. State the number of protons, neutrons and electrons it contains.” Their response addresses only this point: “States 17 protons (equal to the atomic number).” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 5.
Chlorine contains 75% chlorine-35 and 25% chlorine-37. Calculate its relative atomic mass.
[3 marks] - 6.
Marking analysis: A learner attempts the following task: “Chlorine contains 75% chlorine-35 and 25% chlorine-37. Calculate its relative atomic mass.” Their response addresses only this point: “Uses a weighted-average calculation with the given percentages as weights.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] - 7.
Write the full electron configuration of a phosphorus atom (atomic number 15) using subshell notation.
[3 marks] · no calculator - 8.
Marking analysis: A learner attempts the following task: “Write the full electron configuration of a phosphorus atom (atomic number 15) using subshell notation.” Their response addresses only this point: “Fills 1s² 2s² 2p⁶ correctly (10 electrons).” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 9.
Explain why successive ionization energies of an element always increase, and how a large jump between two successive values provides evidence for electron shell structure.
[3 marks] · no calculator - 10.
Marking analysis: A learner attempts the following task: “Explain why successive ionization energies of an element always increase, and how a large jump between two successive values provides evidence for electron shell structure.” Their response addresses only this point: “States that each successive electron is removed from an increasingly positively charged ion, requiring more energy.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 11.
Calculate the number of moles in 5.85 g of sodium chloride, NaCl. Use Ar: Na = 23.0, Cl = 35.5.
[3 marks] - 12.
Marking analysis: A learner attempts the following task: “Calculate the number of moles in 5.85 g of sodium chloride, NaCl. Use Ar: Na = 23.0, Cl = 35.5.” Their response addresses only this point: “Calculates Mr(NaCl) = 23.0 + 35.5 = 58.5.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] - 13.
State Avogadro's constant and use it to calculate the number of molecules in 0.25 mol of water.
[3 marks] - 14.
Marking analysis: A learner attempts the following task: “State Avogadro's constant and use it to calculate the number of molecules in 0.25 mol of water.” Their response addresses only this point: “States Avogadro's constant as 6.02 × 10²³ per mole.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] - 15.
Outline why successive ionization energies show a general increasing trend across each shell, but sub-shell structure (s, p) causes small irregularities within a shell.
[2 marks] · no calculator - 16.
Marking analysis: A learner attempts the following task: “Outline why successive ionization energies show a general increasing trend across each shell, but sub-shell structure (s, p) causes small irregularities within a shell.” Their response addresses only this point: “States that within a shell, ionization energy generally increases as electrons are removed from progressively more stable (lower-energy) sub-shells.” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[2 marks] · no calculator - 17.
Calculate the empirical formula of a compound containing 40% carbon, 6.7% hydrogen and 53.3% oxygen by mass. Use Ar: C = 12, H = 1, O = 16.
[4 marks] - 18.
Marking analysis: A learner attempts the following task: “Calculate the empirical formula of a compound containing 40% carbon, 6.7% hydrogen and 53.3% oxygen by mass. Use Ar: C = 12, H = 1, O = 16.” Their response addresses only this point: “Divides each percentage by its relative atomic mass: C = 40/12 = 3.33, H = 6.7/1 = 6.7, O = 53.3/16 = 3.33.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] - 19.
A mass spectrum of an element shows two peaks: one at mass/charge 63 (69.2%) and one at 65 (30.8%). Identify what these two peaks represent and calculate the relative atomic mass of the element.
[4 marks] - 20.
Marking analysis: A learner attempts the following task: “A mass spectrum of an element shows two peaks: one at mass/charge 63 (69.2%) and one at 65 (30.8%). Identify what these two peaks represent and calculate the relative atomic mass of the element.” Their response addresses only this point: “States that the two peaks represent two different isotopes of the same element.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] - 21.
Calculate the volume occupied by 0.75 mol of oxygen gas at standard temperature and pressure (STP), given that 1 mole of any gas occupies 22.7 dm³ at STP.
[2 marks] - 22.
Marking analysis: A learner attempts the following task: “Calculate the volume occupied by 0.75 mol of oxygen gas at standard temperature and pressure (STP), given that 1 mole of any gas occupies 22.7 dm³ at STP.” Their response addresses only this point: “Uses volume = moles × 22.7 dm³.” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[2 marks] - 23.
Calculate the percentage by mass of nitrogen in ammonium nitrate, NH₄NO₃. Use Ar: N = 14, H = 1, O = 16.
[4 marks] - 24.
Marking analysis: A learner attempts the following task: “Calculate the percentage by mass of nitrogen in ammonium nitrate, NH₄NO₃. Use Ar: N = 14, H = 1, O = 16.” Their response addresses only this point: “Calculates Mr(NH₄NO₃) = 14 + 4(1) + 14 + 3(16) = 80.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] - 25.
Write the electron configuration of the Na⁺ ion (sodium, atomic number 11), and state which noble gas has the same electron configuration.
[3 marks] · no calculator - 26.
Marking analysis: A learner attempts the following task: “Write the electron configuration of the Na⁺ ion (sodium, atomic number 11), and state which noble gas has the same electron configuration.” Their response addresses only this point: “States the electron configuration of the neutral sodium atom: 1s² 2s² 2p⁶ 3s¹.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 27.
Describe and explain the general trend in first ionization energy across period 3 (Na to Ar), in terms of nuclear charge and atomic radius.
[3 marks] · no calculator - 28.
Marking analysis: A learner attempts the following task: “Describe and explain the general trend in first ionization energy across period 3 (Na to Ar), in terms of nuclear charge and atomic radius.” Their response addresses only this point: “States that first ionisation energy generally increases across the period from Na to Ar.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 29.
Explain why first ionization energy decreases down group 1 of the periodic table (Li to Cs), in terms of atomic radius and shielding.
[3 marks] · no calculator - 30.
Marking analysis: A learner attempts the following task: “Explain why first ionization energy decreases down group 1 of the periodic table (Li to Cs), in terms of atomic radius and shielding.” Their response addresses only this point: “States that atomic radius increases down the group, as electrons occupy additional shells further from the nucleus.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator