advanced higher chemistry - kingussie high school

Advanced Higher Chemistry,Unit 1Electronic Structure and the Periodic Table,Some chemistry of thePeriodic Tablea) 2nd & 3rd short periods- oxides, chlorides and hydrides,Chemistry of the oxides, chlorides and hydrides,Looking at the second and third periods, their chemistry can be explained in terms of their structure and type of bonding:,Melting points Boiling points Electrical conductivities,We will look at each family of compounds in turn,The oxides,Forming metal oxides,What is oxygens electronegativity?What is EN roughly when it reacts with group 1, period 2 & 3 metals?What prediction can you make about their bonding types?Which compounds are produced?What do you know about their chemical properties?,Sodium oxide lights used on USS JFK,http:/bubblare.no/sodium_burning_in_air/,Watch the video clip of sodium reacting in air to form sodium oxide,Movement of ions in an ionic crystal at RT,Metal oxides- properties,What properties do typical ionic substances have?,high melting and boiling points look up your data book conductors of electricity when molten and in aqueous solution,Metal oxides- water,These substances are called ionic oxides and tend to be basic;,Na2O(s)+H2O(l) 2NaOH(aq),This can be expressed as a general equation;,O2(s)+H2O(l)2OH(aq),/wiki/Oxides,Potassium hydroxide pellets before dissolving in water,Aluminium oxide- amphoteric,Al2O3 (and beryllium oxide, BeO) react as a typical basic oxide when it reacts with hydrochloric acid to form the salt, aluminium chloride, and water:,Al2O3 + 6HCl 2AlCl3 + 3H2O,Aluminium oxide also behaves as an acidic oxide when it reacts with alkalis such as sodium hydroxide solution: Al2O3 + 3H2O + 2NaOH 2NaAl(OH)4,/wiki/Aluminium_chloride,Forming non-metal oxides,1. What is oxygens electronegativity?2. What is EN roughly when it reacts with group 6 & 7, period 2 & 3 metals?3. What prediction can you make about their bonding types?4. Which compounds are produced?5. What do you know about their chemical properties?,covalent or polar covalent bonding low melting and boiling points look up your data book are gases exist as discrete molecules (SO2, NO2, CO2, CO)*not SiO2. non-conductors of electricity,Non-metal oxides- water,if soluble they dissolve in water to form acids,e.g. sulphur dioxide dissolves in water to form sulphurous acid:,carbon dioxide, CO2, and nitrogen dioxide, NO2 are also acidic,Exception is carbon monoxide, CO, which is a neutral oxide.,Pupil ActivitiesCollect the handouts- trends in the second and third periods, oxides,SO2(g)+H2O(l)H2SO3(aq),Carbon monoxide concentrations,In USA 77% CO emissions are from transportation (mainly cars),In other countries, high CO linked to seasonal agricultural burning. Effects far from source as CO molecules last weeks to months,Silicon dioxide,Exception to molecular structure- SiO2,giant covalent network or lattice structure ratio of silicon to oxygen atoms is 1:2 so the formula, SiO2, is the simplest or empirical formula, not the molecular formula,not soluble in water will dissolve in alkalis to form the silicate ion and so can be considered as an acidic oxide,Quartz, amythest var.,The oxides- pH summary,Metal oxides tend to be basic Non-metal oxides tend to be acidic Amphoteric oxides exhibit both acidic and basic properties,Pupil ActivitiesObserve the reactions of a range of oxides with water.Prepare a sample of aluminium hydroxide and observe its reaction with dilute acid and alkali.,The chlorides,The chlorides of the electropositive metals tend to be ionic and can be made by the direct combination of the elements;,Chlorides are also made by reacting the metal with hydrochloric acid, e.g. Mg(s)+2HCl(aq)MgCl2(aq) +H2(g),Mg(s)+Cl2(g) MgCl2(s),Chlorine is also a very electronegative element The bonding present in the chlorides of the elements in periods 2 & 3 varies in a similar way to that of the oxides Their physical properties can also be described as periodic,/wiki/Category:Chlorides,Ionic chlorides- water,Ionic chlorides of the Group 1 elements dissolve in, but do not react with, water. Retrieved by evaporation;NaCl(s)+aqNaCl(aq),Collecting sea salt, Cape Verde, Canary Islands,Covalent chlorides- water,Going from left to right across a period the electronegativities of the elements increase and so the chlorides become less ionic and more covalent.,Pupil ActivitiesCollect the handouts- trends in the second and third periods, chlorides,Some covalent chlorides are hydrolysed in water and white fumes of hydrogen chloride gas are given off.,The hydrogen chloride also dissolves to give an acidic solution;PCl5(s)+4H2OH3PO4(aq)+5HCl(aq),Aluminium chloride,does not have ionic bonding is hydrolysed in water, producing white fumes of hydrogen chloride solid aluminium chloride sublimes in the vapour state it exists as a dimer with the molecular formula Al2Cl6.,One example is Aluminium chloride,The chlorides- pH summary,Most ionic chlorides dissolve in water without reaction but some covalent chlorides are hydrolysed, producing fumes of hydrogen chloride.,Demonstrate the preparation of a metal chloride and a non-metal chloride.Observe the reactions of a range of chlorides with water.,Forming hydrides,1. What is hydrogens electronegativity?2. What is EN roughly when it reacts with group 1 & 2?3. What prediction can you make about their bonding types?,Ionic hydrides are formed directly from their elements, eg sodium hydride is formed by reacting liquid sodium with hydrogen:,Na(l) + H2(g) Na+H- (s),Pupil ActivitiesCollect the handouts- trends in the second and third periods, hydrides,Structures,Alkali hydrides form ionic solids and take on the sodium chloride (fcc) type structural lattice:,A) Lithium HydrideB) Sodium HydrideC) Potassium HydrideD) Potassium Hydrino (1/4) Hydride,Ionic hydrides- water,2NaH(s) + 2H2O(l) H2(g) + 2Na+OH-(aq),The hydride ion is a strong base and ionic hydrides react by removing a hydrogen ion from a water molecule:,Producing hydrogen gas and hydroxide ions,Sodium hydride is used in some fuel cells as source of hydrogen gas,On reaction with water ionic hydrides produce hydrogen gas and the hydroxide ion.,How?,Ionic hydrides- Uses,Ionic hydrides possess the hydride ion which acts as a reducing agent.,Why?,More complex hydrides are now more commonly used (Unit 3): lithium aluminium hydride, LiAlH4 sodium tetrahydroborate, NaBH4,Look at the previous reaction!Simple hydrides are used in the lab as reducing and drying agents,Industrially NaH and CaH2 are sometimes used as drying agents as they are easily handled and relatively cheap,Electrolysis of hydrides,Electrolysis of molten ionic hydrides produces hydrogen gas at the positive e