OCR A Level Chemistry B (Salters)
OCR A Level Chemistry B Elements of Life (EL) Exam Questions
Free OCR A Level Chemistry B exam questions for Elements of Life (EL), with a mark scheme for every pack. Covers atomic structure, isotopes, mass spectra, amount of substance, electronic structure, emission and absorption spectra, bonding, shapes and Group 2 chemistry.
Elements of Life (EL) exam questions
4 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About OCR A Level Chemistry B Elements of Life (EL)
Elements of Life is the opening storyline of OCR A Level Chemistry B (Salters). It uses the story of the elements in the human body and in stars to introduce atomic structure, isotopes and mass spectrometry, the mole and amount of substance calculations, electronic structure in shells and subshells, and atomic spectra. It also covers ionic and covalent bonding, shapes of molecules and the chemistry of Group 2. Because it sets up the language and calculations for every later storyline, examiners test it heavily through definitions, titration and mole calculations, explanations of spectra in terms of energy levels, and Group 2 trends.
What you need to know
- Atoms and isotopes Protons, neutrons and electrons; isotopes and relative isotopic mass; relative atomic mass calculated from mass spectra; nuclear fusion in stars forming heavier elements.
- Amount of substance Moles, the Avogadro constant, empirical formulae, reacting masses, concentrations in mol dm-3 and titration calculations, including making a standard solution.
- Electronic structure Shells, subshells (s, p, d) and orbitals; electron configurations up to krypton; blocks of the periodic table and periodic trends.
- Atomic spectra Electrons absorb energy and move to higher energy levels; when they fall back they emit photons of specific frequencies, giving line spectra. Delta E = hf links the energy gap to frequency, and c = f x wavelength.
- Bonding and shapes Ionic, covalent and dative covalent bonding; electron pair repulsion to predict shapes such as tetrahedral, pyramidal, bent, linear and octahedral.
- Group 2 Reactions of Group 2 elements and oxides with water; solubility of hydroxides and carbonates; thermal stability of carbonates increases down the group.
Common mistakes in Elements of Life (EL)
- Saying line spectra come from electrons gaining energy. Emission lines come from electrons falling to lower levels; absorption lines from electrons absorbing specific frequencies.
- Forgetting to convert frequency or wavelength units, for example nm to m, before using delta E = hf and c = f x wavelength.
- Rounding too early in titration calculations or using a non-concordant titre in the mean.
- Writing electron configurations with 3d filled before 4s for atoms such as potassium and calcium.
- Saying Group 2 carbonates become less stable down the group. Thermal stability increases down the group.
Try three Elements of Life (EL) exam-style questions
1. 0.486 g of magnesium reacts with excess hydrochloric acid. Calculate the volume of hydrogen formed at room temperature and pressure. (Ar Mg = 24.3; molar gas volume = 24.0 dm3 mol-1) (2 marks)
Show the mark scheme answer
Moles Mg = 0.486 / 24.3 = 0.0200 mol, and Mg + 2HCl gives MgCl2 + H2 so moles H2 = 0.0200 mol; volume = 0.0200 x 24.0 = 0.480 dm3.
2. Explain how the emission spectrum of hydrogen provides evidence for energy levels in atoms. (3 marks)
Show the mark scheme answer
The spectrum consists of lines at specific frequencies; each line is produced when an electron falls from a higher to a lower energy level, emitting a photon with energy delta E = hf; because only certain frequencies appear, electrons can only have certain fixed energies.
3. Write the electron configuration of calcium and of the Ca2+ ion. (2 marks)
Show the mark scheme answer
Ca: 1s2 2s2 2p6 3s2 3p6 4s2; Ca2+: 1s2 2s2 2p6 3s2 3p6.
Elements of Life (EL) FAQs
What does OCR A Level Chemistry B Elements of Life (EL) cover?
It covers atomic structure and isotopes, mass spectra, amount of substance and titrations, electronic structure, emission and absorption spectra, bonding and shapes, and Group 2 chemistry.
Which papers is Elements of Life examined in?
In the Salters A Level, content from any storyline can be assessed in all three papers: Fundamentals of chemistry, Scientific literacy in chemistry and Practical skills in chemistry.
What equations do I need for Elements of Life?
You need n = m / M, n = cV, molar gas volume, delta E = hf and c = f x wavelength, plus the method for calculating relative atomic mass from isotopic abundances.
