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Chem unit 1 pastpap4
| Question | Answer |
|---|---|
| State how you could find the molecular mass of a substance from its mass spectrum. | (Molecular mass of a substance is) that of the molecular ion/parent ion OR (m/e value for) peak/ion of largest mass OR (m/e value for) peak/ion furthest to |
| Suggest how mass spectrometry can be used to estimate the age of the cloth. | Any mention of amount /mass/abundance of 14C (in cloth)find proportion of 12C : 14C (in cloth). find proportion of 12C : 14C (in cloth) |
| Explain why the melting temperature of sodium is very much less than that of Magnesium | odium atoms/sodium ions are larger (than magnesium atoms/ions) OR Na+/sodium ions have smaller charge (density) than Mg2+/ magnesium ions |
| Explain why the melting temperature of sodium is very much less than that of Magnesium | sodium has fewer delocalized electrons (than magnesium)/attraction between the positive ions and (delocalized) electrons is weaker in sodium (than magnesium) (1) · sodium is not close-packed (but mg is close-packed)/less energy needed (to break bonds) |
| Explain why the melting temperature of silicon is very much greater than that of white phosphorus. | Silicon is giant covalent / giant atomic/giant molecular/ macromolecular/giant/ structure/giant lattice · Phosphorus made up of simple molecules /small molecules/ P4 |
| Explain why the melting temperature of silicon is very much greater than that of white phosphorus. | P4 is molecular covalent /molecular/simple covalent/ Between P4 molecules: weak forces/weak intermolecular forces/weak London forces/weak van der Waals’ forces/weak dispersion forces/weak induced-dipole forces /More energy needed (to break). |
| Explain why the melting temperature of argon is the lowest of all the elements of Period 3. à | Argon monatomic/argon (composed of) single atoms |
| Explain why magnesium is a good conductor of electricity whereas sulfur is a non-conductor | Mg has mobile electrons/delocalized electrons/free electrons/sea of electrons (to carry the charge) ALLOW Mg2+ instead of Mg or Magnesium, |
| Explain why magnesium is a good conductor of electricity whereas sulfur is a non-conductor | ulfur’s electrons are fixed (in covalent bonds)/sulfur’s electrons are involved in bonding/sulfur’s electrons are not free (to move)/no delocalized electrons in sulfur/no mobile electrons in sulphur. |
| Describe the forces of attraction in an ionic lattice à | (Forces of attraction between) oppositely-charged ions/positive and negative ions/cations and anions. |
| Suggest two forces of repulsion which exist in an ionic lattice à | Ions of the same charge (repel)/ positive ions (repel)/negative ions (repel). Nuclei (of the ions repel) ALLOW ‘protons’ (in the ions repel) OR Electron clouds OR electrons (in the ions repel). |
| Suggest two forces of repulsion which exist in an ionic lattice à | The lattice composed of the ions Mg2+ and O2– is stronger than a lattice composed of the ions Mg+ and O– |
| Explain, in terms of the charges on the ions and the size of the cations, why this is so. | Mg2+ AND O2− higher charge / Mg2+ AND O2− higher charge density (than Mg+ and O−) NOTE: both ions needed (1) Second mark: Mg2+ smaller (than Mg+). |
| Suggest how the lattice energy of Mg2+O2– would differ from that of Mg+O–.--> | (Lattice energy of Mg2+O2- is) more exothermic/more negative ALLOW greater/increased/higher/ more/larger/bigger. |
| Explain the difference between hazard and risk. | (substance or procedure that) can cause harm/may cause harm/has the potential to do harm/can be dangerous |
| Explain the difference between hazard and risk. | references to specific hazards such as toxic/flammable /harmful/ irritant /corrosive /oxidizing/ carcinogenic. idea of likelihood/probability/chance that harm will result (from the use of a substance or a procedure). |
| Give one other safety procedure ,other than the use of a laboratory coat and safety goggles. | --> fume cupboard OR Gloves OR u.v. goggles. |
| Why is a compound with this general formula not a alkene. --> | (CnH2n could be a) ring / cyclic (compound) |
| Which of the following alkenes exhibits E-Z isomerism?--> | H3CCH=CHCH3 |
| Which of the following substances, obtained from the fractional distillation of crude oil, has the lowest boiling temperature? --> | refinery gas. |
| Which of the following ions would undergo the greatest deflection in a mass spectrometer? --> | 35Cl2+ |
| Which pair of atomic numbers represents elements which are both in the p-block of the Periodic Table? --> | 8, 16. |
| The electronic structure of an atom of an element in Group 6 of the Periodic Table could Be --> | 1s2 2s2 2p4 |
| Which of the following formulae for compounds of germanium, Ge, is unlikely to be correct, given the position of germanium in the Periodic Table? --> | GeF3 |
| Which of the following covalent bonds is the shortest --> | H—F |
| The electronic configurations of the atoms of four different elements are given below. For which element would you expect the value of the first ionization energy to be the largest?--> | 1s2. |
| Which of the following has the smallest ionic radius? --> | Mg2+ |
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ufuoma
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