A LEVEL 化学A2-Group IV第四主族元素 (2) worksheet with answers.doc

A2 Chemistry Group IV (2) answer1. (a) The melting points of some oxides of Group IV elements are given below.Describe the bonding in each oxide, and how it relates to its melting point.(i) CO2Covalent bondsWeak V.D.W. forces among molecules, hence m.p. is low.(ii) SiO2Covalent bondsGiant covalent structure, hence m.p. is high.(iii) SnO2Covalent bonds with ionic characterGiant covalent structure, hence m.p. is high.(b) Writing balanced equations where appropriate, describe how the above three oxides differ in their reactions with(i) NaOH(aq),CO2 + 2NaOH Na2CO3 + H2OSiO2 + 2NaOH Na2SiO3 + H2OSnO2 + 2NaOH Na2SnO3 + H2O(ii) HCl(aq).SnO2 + 4HCl SnCl4 + 2H2O(c) The last oxide in Group IV, PbO2, reacts with concentrated hydrochloric acid liberating chlorine gas. Use the Data Booklet to calculate the cell and to write a balanced equation for this reaction.PbO2 + 4HCl PbCl2 + 2H2O + Cl2cell = 1.47 1.36 = 0.11 V2. Carbon forms two stable oxides, CO and CO2. Lead forms three oxides: yellow PbO, black PbO2 and red Pb3O4.(a) Carbon monoxide burns readily in air. Heating black lead oxide produces oxygen gas, leaving a yellow residue.(i) Suggest a balanced equation for each reaction.2CO + O2 2CO2PbO2 2PbO + O2(ii) Explain how these two reactions illustrate the relative stabilities of the +2 and +4 oxidation states down Group IV.+4 state becomes less stable down the group(or +2 state becomes more stable down the group)(iii) How can this relative stability of the +2 and +4 oxidation states be related to the bonding in the Group IV oxides?The Group IV oxides (+2) tend to have more ionic character down the group.The Group IV oxides (+4) tend to have more covalent character down the group.(b) Red lead oxide contains lead atoms in two different oxidation states.(i) Suggest what these oxidation states are, and calculate the ratio in which they occur in red lead oxide.Pb(II) : Pb(IV) = 2:1(ii) Predict the equation for the action of heat on red lead oxide.2Pb3O4 6PbO + O2 When red lead oxide is heated with dilute nitric acid, HNO3, a solution of lead (II) nitrate is formed and a black solid is left.(iii) Suggest an equation for this reaction.Pb3O4 + 4HNO3 2Pb(NO3)2 + PbO2 + 2H2O(iv) Explain how this reaction illustrates the relative basicities of the two oxidation states of lead.Pb(II) is more basic than Pb(IV)as PbO2 does not react with HNO3(c) Both tin (II) oxide and tin (IV) oxide are amphoteric.Write a balanced equation for the reaction between tin (II) oxide and aqueous sodium hydroxide.SnO + 2NaOH Na2SnO2 + H2O3. The table below shows the acidbase character of the Group IV oxides in oxidation state +4.Oxidation state +4Acidbase characterCO2acidicSiO2very weakly acidicGeO2SnO2amphotericPbO2amphoteric(a) Write a balanced equation for the reaction of SnO2 with hydrochloric acidSnO2 + 4HCl SnCl4 + 2H2O(ii) Write a balanced equation for the reaction of SnO2 with sodium hydroxide to form sodium stannate (IV), which contains the SnO32- ion.SnO2 + 2NaOH Na2SnO3 + H2O(b) Suggest the acidbase character of GeO2.Amphoteric4. Germanium is an element in Group IV of the Periodic Table. It forms a number of compounds including GeCl4, GeO and GeO2.(a) (i) Draw a diagram to show the 3D structure of germanium (IV) chloride.(ii) State the value of the Cl-Ge-Cl bonds angle in germanium (IV) chloride.109.5(b) Explain why germanium (IV) chloride has a low boiling point. GeCl4 has a simple molecular structure;V.D.W. forces keeping the molecules together are weakLittle energy required to overcome the weak attractive forces(c) Germanium (IV) chloride is hydrolyzed by water. Write a balanced equation for this reaction.GeCl4 + 2H2O GeO2 + 4HCl(d) Germanium (II