2.5. Simple molecules and covalent bonds
A subsection of Chemistry, 0620, through 2. Atoms, elements and compounds
Listing 10 of 177 questions
The diagrams show part of the structures of five substances, A, B, C, D and E. Li+ Cl – Li+ Cl – Cl – Li+ Li+ Cl – Li+ Cl – Li+ Cl – Cl – Li+ Li+ Cl – Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu He He He He He He A B D E C N N N N N N N N N N Answer the following questions about these structures. Each structure may be used once, more than once or not at all. Which two of these structures, A, B, C, D or E, are covalently bonded? and  Which one of these structures, A, B, C, D or E, is a diatomic molecule? Which one of these structures, A, B, C, D or E, is a compound? Which one of these structures, A, B, C, D or E, is very soluble in water? Which one of these structures, A, B, C, D or E, is used in cutting tools? Which one of these structures, A, B, C, D or E, is used in electrical wiring? Substance B is an element. What is meant by the term element ? 
0620_s19_qp_31
THEORY
2019
Paper 3, Variant 1
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The structure of compoundS is shown. C C C C H O O H H H H H O C C C Draw a circle around the carboxylic acid functional group in this structure. How many different types of atom are shown in this structure? The melting point of pure S is 159 °C. The boiling point of pure S is 200 °C. What is the physical state of pure S at 100 °C? Explain your answer. Which one of these statements about an impure sample of compoundS is correct? Tick one box. The melting point of impure S is 159 °C and the boiling point is above 200 °C. The melting point of impure S is below 159 °C and the boiling point is 200 °C. The melting point of impure S is 159 °C and the boiling point is 200 °C. The melting point of impure S is below 159 °C and the boiling point is above 200 °C.  Aqueous ethanoic acid has chemical properties which are typical of acids. Describe two chemical properties of aqueous ethanoic acid.  Ethanol can be converted into ethene by passing ethanol vapour over a catalyst of aluminiumoxide. C2H5OH C2H4 + X Identify compound X. Explain why a catalyst is used. Draw the structure of a molecule of ethanol. Show all of the atoms and all of the bonds.  Ethene can be polymerised. State the name of the polymer formed from ethene. Terylene is also a polymer. State one use of Terylene. 
0620_s19_qp_33
THEORY
2019
Paper 3, Variant 3
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This question is about phosphorus and compounds of phosphorus. Phosphorus has the formula P4. Some properties of P4 are shown. melting point / °C boiling point / °C electrical conductivity non-conductor solubility in water insoluble Name the type of bonding that exists between the atoms in a P4 molecule. Explain, in terms of attractive forces between particles, why P4 has a low melting point. Explain why phosphorus is a non-conductor of electricity. Phosphorus, P4, reacts with air to produce phosphorus(oxide, P4O10. Write a chemical equation for this reaction. What type of chemical reaction is this? Phosphorus(oxide, P4O10, is an acidic oxide. Phosphorus(oxide, P4O10, reacts with aqueous sodiumhydroxide to form a salt containing the phosphate ion, PO4 3–. Water is the only other product. Write a chemical equation for the reaction between phosphorus(oxide and aqueous sodiumhydroxide. Phosphine has the formula PH3. Complete the dot-and-cross diagram to show the electron arrangement in a molecule of phosphine. Show outer shell electrons only. P H H H  Phosphine, PH3, has a similar chemical structure to ammonia, NH3. Ammonia acts as a base when it reacts with sulfuric acid. What is meant by the term base? Write a chemical equation for the reaction between ammonia and sulfuricacid. 
0620_s19_qp_42
THEORY
2019
Paper 4, Variant 2
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Fluorine forms both ionic and covalent compounds. Magnesium reacts with fluorine to form the ionic compound magnesiumfluoride. The electronic structures of an atom of magnesium and an atom of fluorine are shown. Mg F Complete the dot-and-cross diagrams to show the electronic structures of one magnesium ion and one fluoride ion. Show the charges on the ions. Mg F  What is the formula of magnesiumfluoride? Magnesiumfluoride does not conduct electricity when it is solid. What can be done to solid magnesiumfluoride to make it conduct electricity? In your answer explain why magnesiumfluoride conducts electricity when this change is made. Carbonyl fluoride, COF2, is a covalent compound. The structure of a molecule of COF2 is shown. C O F F Complete the dot-and-cross diagram to show the electron arrangement in a molecule of carbonylfluoride. Show outer shell electrons only. C O F F  The melting points of magnesiumfluoride and carbonylfluoride are shown. melting point / °C magnesium fluoride carbonyl fluoride –111 Explain, using your knowledge of structure and bonding, why magnesiumfluoride has a high melting point. Explain, using your knowledge of structure and bonding, why carbonylfluoride has a low melting point. 
0620_s20_qp_42
THEORY
2020
Paper 4, Variant 2
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Magnesium forms ionic compounds. Magnesium reacts with fluorine to form the ionic compound magnesium fluoride. The electronic configurations of an atom of magnesium and an atom of fluorine are shown in Fig.3.1. fluorine atom magnesium atom F Mg Ions are formed by the transfer of electrons from magnesium atoms to fluorine atoms. Complete the dot-and-cross diagrams in Fig.3.2 to show the electronic configurations of one magnesium ion and one fluoride ion. Show the charges on the ions. F Mg fluoride ion magnesium ion  Deduce the formula of magnesiumfluoride. When solid magnesiumfluoride is dissolved in water it forms a solution that conducts electricity. State one other change that can be made to solid magnesiumfluoride to allow it to conduct electricity. Silicontetrachloride, SiCl 4, and silicon(oxide, SiO2, are covalent compounds. Complete the dot-and-cross diagram in Fig. 3.3 to show the electronic configuration in a molecule of silicontetrachloride. Show outer shell electrons only. Si Cl Cl Cl Cl  The melting points of silicontetrachloride and silicon(oxide are shown in Table3.1. Table 3.1 melting point / °C silicon tetrachloride –69 silicon(oxide Silicon tetrachloride has a low melting point because it has weak forces of attraction between particles. Name the type of particles that are held together by these weak forces of attraction. Explain, in terms of structure and bonding, why silicon(oxide has a high melting point. 
0620_s23_qp_43
THEORY
2023
Paper 4, Variant 3
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shows the structures of seven substances, A, B, C, D, E, F and G. A B C D E F G H N H H H C H H O H O O H C H N N O O Cl – Cs+ Cl – Cs+ Cl – Cs+ Cl – Cs+ Cl – Cs+ Cl – Cs+ Answer the following questions using only the structures in . Each structure may be used once, more than once or not at all. State which structure represents: a gas that forms 78% by volume of clean, dry air a compound with a high melting point a giant covalent structure a compound in the same homologous series as ethanol a product of photosynthesis a non-metallic element that conducts electricity. Complete to show the dot-and-cross diagram for structure G. Show the outer electron shells only. N H H H , ,
0620_s24_qp_32
THEORY
2024
Paper 3, Variant 2
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