REACTIONS OF PERIOD 3 ELEMENTS WITH WATER

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1 QUESTINSHEET 1 REACTINS F PERID 3 ELEMENTS WITH WATER a) (i) Sodium melts into a ball / heat is given out Effervescence / gas evolved Sodium skates across the surface Ignition may occur Maximum 3 marks Quality of language: two or more sentences with correct spelling, punctuation and grammar in which the meaning is clear. (ii) 2Na(s) + 2 (l) 2NaH(aq) + (g) (iii) (iv) Redox / oxidation-reduction b) (i) Less reactive / less powerful reducing agents / higher ionisation energies / lower in electrochemical series / less ve Eê values (ii) Pass steam over the heated metal

2 a) QUESTINSHEET 2 REACTINS F PERID 3 ELEMENTS WITH XYGEN Na Mg Al Si P S Reaction conditions Ignite in air or 2 Heat in 2 Ignite in air or 2 Formula of oxide (or lower oxide) Na 2 Mg Al 2 3 Si 2 P 4 6 or (½) (½) (½) (½) P 2 3 (½) S 2 (½) b) (i) 4Na + 2 2Na 2 (6) (ii) 2Mg + 2 2Mg (iii) 2Al Al 2 3 (iv) Si + 2 Si 2 (v) 2P P 2 3 (vi) S + 2 S 2

3 QUESTINSHEET 3 STRUCTURE AND BNDING F PERID 3 XIDES a) Na 2 Mg Al 2 3 Si 2 P 4 10 S 2 2 Bonding Ionic Covalent Structure Ionic lattice Macromolecular Simple molecular b) From Na 2 Mg Al 2 3 there is an increase in m.p. Reason: ionic bonding becomes stronger (r lattice enthalpy increases in magnitude ) because cations decrease in size (½) and increase in charge (½) (r because surface charge density / charge:radius ratio increases ) Si 2 has the highest m.p. because all / many strong covalent bonds must be broken for it to melt Remainder have low m.p. because the only forces to be overcome on melting are relatively weak intermolecuar forces / van der Waals forces c) Melting point of Mg is higher than that of Ca Reason: the ionic bonding in Mg is stronger than that in Ca (r the lattice enthalpy of Mg is greater than that of Ca ) because Mg 2+ is smaller than Ca 2+ / Mg 2+ has a higher charge density

4 QUESTINSHEET 4 PERID 3 XIDES WITH WATER a) xides on LHS react / dissolve in water to give alkaline solutions / ph >7.0 e.g. Na 2 / Li 2 Na 2 (s) + (l) 2NaH(aq) xides further along a period are insoluble in water e.g. Be / Mg / Al 2 3 xides on RHS give acidic solutions / ph < 7.0 e.g. S 2 / S 3 / other acidic oxide S 2 (g) + (l) S 3 (aq) b) Acidity increases with oxygen content / oxidation number C: no reaction with water ph = 7 C 2 (g) + (l) C 3 (aq) ph = 5-6 P 4 6 (s) + 6 (l) 4H 3 P 3 (aq) ph = 2-4 P 4 10 (s) + 6 (l) 4H 3 P 4 (aq) ph = 0-2 Note Examiners may accept equations without state symbols.

5 QUESTINSHEET 5 ACID - BASE CHARACTER F PERID 3 XIDES a) xide Na 2 Mg Al 2 3 Si 2 P 4 6 P 4 10 S 2 S 3 Acid - base character Basic (½) Basic (½) Amphoteric Acidic (½) Acidic (½) Acidic (½) Acidic (½) b) Mg(s) + S 4 (aq) MgS 4 (aq) + (l) Al 2 3 (s) + 6H(aq) 2Al 3 (aq) + 3 (l) Al 2 3 (s) + 2NaH(aq) + 7 (l) 2Na[Al(H) 4 ) 2 ](aq) Accept Na[Al(H) 4 ] S 3 (s) + 2NaH(aq) Na 2 S 4 (aq) + (l) r S 3 (s) + NaH(aq) NaHS 4 (aq) Accept similar equations for S 2 (g) (Throughout, accept similar equations for other acids and bases. Examiners may accept equations without state symbols) c) Mg H + 2- accepts protons and is therefore a base on the BrØnsted-Lowry theory r donates lone pairs of electrons to H + and is therefore a base on the G.N. Lewis theory S 3 S 3 + 2H - S r S 3 + H - HS 4 - S 3 accepts a lone pair of electrons from H - and is therefore an acid on the G.N. Lewis theory (Accept similar explanation for S 3 +, or for S 2 with either H - or )

6 QUESTINSHEET 6 a) (i) Signs must be given. (ii) More stable state of tin is +4 More stable state of lead is +2 b) (i) Sn 2 Reducing agent Pb 2 Neither Sn 2 Neither Pb 2 xidising agent STABILITY F GRUP 4 XIDATIN STATES (ii) Accept Sn 2 with KMn 4, K 2 Cr 2 7, Fe 3, Hg 2, C 6 H 5 N 2, etc. Correct reactant Correct product Accept Pb 2 with conc H(aq), Na 3 [Cr(H) 6 ] etc. Correct reactant Correct product c) +2 state increases in stability because this is essentially an ionic state / M 2+ ions are concerned Ionisation energies decrease / ions are formed more easily on descending the group +4 state decreases in stability because energy is needed to promote an ns electron to a vacant np orbital and, for larger atoms, less energy is released when (weak) covalent bonds are formed

7 QUESTINSHEET 7 HYDRLYSIS F GRUP 4 CHLRIDES a) (i) Si 4 (l) + 2 (l) Si 2 (aq)(s) + 4H(aq) H H Si H Si + H Repeated 3 Si 2-2 Si(H) 4 (ii) cannot coordinate to the C atom / nucleophilic attack by cannot occur because C does not have a vacant orbital in its outer shell / 2d orbital to accept a lone pair b) (i) bservation A white suspension / cloudy solution Equation Sn 2 (aq) + (l) Sn(H)(s) + H(aq) Prevention By adding hydrochloric acid which disturbs equilibrium to the LHS (ii) Pb 2 has an ionic structure but Sn 2 is predominantly covalent With acting as a nucleophile, substitution occurs Examiners may accept equations without state symbols.

8 QUESTINSHEET 8 DEFINITINS AND ELECTRNIC CNFIGURATINS a) A d-block element is one with its highest energy electron in a d-orbital A transition element is one which can form one or more stable ions with a partially occupied d-subshell b) (i) Yes Configuration is [Ar] 3d 1 4s 2 (ii) No Its only cation has the configuration [Ar] 3d 0 4s 0 c) (i) 3d 4s 4p Cu [Ar] Cu 2+ [Ar] Cr [Ar] Cr 3+ [Ar] (ii) Unusual feature Their atoms have only one 4s electron while atoms of other transition elements have two 4s electrons Reason for copper Configuration as shown rather than [Ar] 3d 9 4s 2 because of exceptional stability associated with a fully occupied 3d subshell Reason for chromium Configuration as shown rather than [Ar] 3d 4 4s 2 because there is no mutual electrical repulsion in any orbital and the electron spin is parallel / [Ar] 3d 5 4s 1 is a more stable electronic configuration d) (i) Iron(III) ion Manganese(II) ion Accept Fe 3+ & Mn 2+ (ii) Half-filled 3d subshell

9 QUESTINSHEET 9 BNDING IN CMPLEX INS a) (i) A molecule or anion which can donate one or more lone pairs of electrons to a cation (ii) Complex cation Species with a positive charge formed from ligands bonded to a central cation Example [Ag( ) 2 ] + or any other b) (i) Complex anion Species with a negative charge formed from ligands bonded to a central cation Example [Fe(CN) 6 ] 4- or any other III Cr 3+ (2) Deduct 1 mark if charge is missing ctahedral shape (ii) Coordinate / dative covalent (iii) Lone pair of electrons on the atom of a molecule Cr 3+ ion has vacant orbitals which can accept 6 pairs of electrons (iv) 3d 4s 4p [Ar] Electrons possessed by Cr 3+ ion. Electrons originating from the ligands for unpaired electrons for electron pairs for labels

10 QUESTINSHEET 10 CLUR F CMPLEX INS a) IN Cr 3+ (aq) Mn 2+ (aq) Fe 2+ (aq) Fe 3+ (aq) Cu 2+ (aq) CLUR green (pale) pink (pale) green yellow blue or purple or brown b) [Cu ] 2+ [Cu 4 ] 2- or other example Blue Yellow or green for formulae for colours c) (i) 3d 4s 4p Ti 4+ [Ar] Cu + [Ar] Zn 2+ [Ar] Ti 2+ [Ar] (ii) nly Ti 2+ (iii) Colour results from the absorption of one or more frequencies of white light in promoting d-electrons from a low energy orbital to a higher energy orbital Not possible if the 3d subshell is empty / rules out Ti 4+ Not possible if the 3d subshell is full / rules out Cu + & Zn 2+ nly Ti 2+ has a partially filled d-subshell Maximum 4 marks

11 QUESTINSHEET 11 ISMERISM a) Test 1 Reagent Ba 2 (aq) / Ba(N 3 ) 2 (aq) bservation with A White (½) precipitate (½) bservation with B No precipitate / solution remains clear Test 2 Reagent AgN 3 (aq) bservation with A No precipitate / solution remains clear bservation with B Cream / off-white / pale yellow (½) precipitate (½) b) (i) A [Pt( ) 6 ] 4+ B [Pt( ) 5 ] 3+ H 3 N H 3 N IV Pt 4+ H 3 N IV Pt 3+ C [Pt 2 ( ) 4 ] 2+ D [Pt 3 ( ) 3 ] + H 3 N IV Pt 2+ IV Pt + Accept cis or trans isomer Accept fac or mer isomer (ii) Dissolve equal masses / amounts of each in water Either Titrate a suitable volume of each with AgN 3 (aq) Titres for A, B, C and D are in the ratio 4 : 3 : 2 : 1 c) (i) r Add excess AgN 3 (aq) to each, then filter, wash, dry and weigh precipitates Masses for A, B, C and D are in the ratio 4 : 3 : 2 : 1 NH 3 H 3 N II Ni trans (½) II Ni cis (½) (ii) H 3 N H 3 N III Co + H 3 N III Co + cis (½) trans (½)

12 QUESTINSHEET 12 LIGAND EXCHANGE REACTINS a) Definition A reaction in which one or more coordinated water molecules is replaced / substituted by other ligands Reason 1 Relatively strong ligands tend to displace weaker ones / water is a weak ligand Reason 2 Ligand exchange is reversible / if a ligand is added in high concentration, equilibrium will be disturbed to RHS Quality of language:two or more sentences with correct spelling, punctuation and grammar in which the meaning is clear. b) (i) Ionic equation [Cu ] 2+ (aq) + 6 (aq) [Cu( ) 6 ] 2+ (aq) + 6 (l) Colour change From blue (½) to royal blue/purple (½) Shape of resulting complex ion ctahedral (ii) Ionic equation [Cu ] 2+ (aq) (aq) [Co 4 ] 2- (aq) + 6 (l) Colour change From blue (½) to green/yellow (½) Shape of resulting complex ion Tetrahedral c) If ligands are relatively large fewer of them can be accommodated around a cation

13 QUESTINSHEET 13 DEPRTNATIN THERY a) (i) ph decreases from 7.0 (ii) Reasons A proton is transferred from [Fe ] 3+ / ligand to a molecule of solvent water Hence [H 3 + ] > [H - ] Maximum 3 marks Equation [Fe ] 3+ (aq) + (l) ¾ [Fe(H) ) 5 ] 2+ (aq) + H 3 + (aq) (Examiners may accept equation without state symbols) (iii) Type of reaction Deprotonation / acid-base Function of hydrated metal ions Acid Function of water molecules Base b) (i) [Fe(H) ) 5 ] 2+ (aq) + (l) ¾ [Fe(H) 2 ) 4 ] + (aq) + H 3 + (aq) [Fe(H) 2 ) 4 ] + (aq) + (l) ¾ [Fe(H) 3 ) 3 ](s) + H 3 + (aq) (Examiners may accept equations without state symbols) (ii) H - is a stronger base than c) (i) Solution is acidic [Cu ] 2+ behaves in a similar manner to [Fe ] 3+ (ii) Fe 3 has the lower ph Fe 3+ has a higher charge than Cu 2+ and is smaller r Fe 3+ has a higher charge density than Cu 2+ (2) Hence Fe 3+ increases polarisation of H bonds which weakens these bonds / facilitates loss of a proton

14 QUESTINSHEET 14 a) (i) Both H - and are bases (ii) Green precipitate (½) Cr(H) 3 (½) White precipitate (½) Mn(H) 2 (½) Green precipitate (½) Fe(H) 2 (½) Brown precipitate (½) Fe(H) 3 (½) Blue precipitate (½) Co(H) 2 (½) Green precipitate (½) Ni(H) 2 (½) Blue precipitate (½) Cu(H) 2 (½) Any 3 Accept full formulae REACTINS F CATINS WITH H - AND b) Excess dilute NaH(aq) Excess (aq) Example of a compound which will dissolve Reason for dissolving Type of reaction occurring Cr(H) 3 Cr(H) 3 is amphoteric Deprotonation / acid-base Co(H) 2 / Ni(H) 2 / Cu(H) 2 (Accept Cr(H) 3 ) is a ligand / ammine formation Ligand exchange / substitution bservation Formula of the ion produced Green solution [Cr(H) 4 ) 2 ] - / [Cr(H) 5 )] 2- / [Cr(H) 6 ] 3- Co II pale brown solution / Ni II blue solution / Cu II dark blue solution [Co( ) 6 ] 2+ / [Ni( ) 6 ] 2+ / Cu( ) 4 ) 2 ] 2+ c) (i) Aluminium hydroxide Lead(II) hydroxide Tin(II) hydroxide Tin(IV) hydroxide Beryllium hydroxide Any 2 (ii) [Al(H) 4 ) 2 ] - [Pb(H) 4 ] 2- [Sn(H) 4 ] 2- [Sn(H) 6 ] 2- [Be(H) 4 ] 2- Any 2

15 QUESTINSHEET 15 XIDATIN STATES a) (i) +6 (ii) +6 (iii) +3 (iv) +5 (v) +5 (vi) +3 (vii) +4 (viii) +3 (ix) +6 (x) +2 (½) each x 10 = 5 marks b) Energy levels of 4s and 3d electrons are very similar hence 3d as well as 4s electrons can be used in bonding Although more energy is required to remove more electrons this is often compensated by the release of latttice enthalpy or hydration enthalpy Maximum 3 marks

16 QUESTINSHEET 16 CLRIMETRY a) (i) Volume of 0.1 M CuS 4 (aq) 20 cm 3 (½) Volume of 0.1 M (aq) 80 cm 3 (½) (ii) n (Cu 2+ ) = 0.1 x 20/1000 = mol n ( ) = 0.1 x 80/1000 = mol mole ratio Cu 2+ : = 1.4 (iii) [Cu( ) 4 ) 2 ] 2+ r [Cu( ) 4 ] 2+

17 QUESTINSHEET 17 LIGAND EXCHANGE AND STABILITY CNSTANTS (a) (i) Yellow colour is a complex with ammonia because the ammonia is a more reactive ligand than water (not sulfate)/ the ammonia complex is more stable the aqua complex. Blue colour is a cyanide complex because the cyanide is a more reactive ligand than ammonia / the cyanide complex is more stable the ammonia complex. No further reaction because ammonia is a less reactive ligand than the cyanide. Allow 1 mark for well constructed answer and use of three terms like: ligand, reactive, powerful, displacement, complex, stable, aqua. (ii) Mauve colour is an ethane-1,2-diamine complex because the ethane-1,2-diamine is a more reactive ligand than ammonia/ the ethane-1,2-diamine complex is more stable the ammonia complex. No further reaction with the yellow cyanide complex because ethane-1,2-diamine is a less reactive ligand than the cyanide. (b) (i) No the complex with ethane-1,2-diamine has a larger stability constant that the EDTA complex. (ii) No the complex with cyanide has a larger stability constant that the ammonia complex. (iii) [Co(CN) 6 ] 3- The cyanide is the more stable complex and is formed in preference to ammonia complex All the [Co ] 3+ has reacted with the cyanide (iv) [Co( )] 3+ The [Co( )] 3+ is the more stable complex and is formed in preference to [Co( )] 2+ complex All the ammonia has reacted with the [Co ] 3+

18 QUESTINSHEET 18 d-rbital SPLITTING AND LIGHT ABSRPTIN a) (i) d x 2 y 2 d x 2 d x 2 y 2 d x 2 Energy Cu 2+ uncomplexed Adding ligands Absorbing light d xy d xz d yz Ground state d xy d xz d yz Excited state (ii) d x 2 y 2 d x 2 d x 2 y 2 d x 2 Energy Fe 3+ uncomplexed Adding ligands Absorbing light d xy d xz d yz Ground state d xy d xz d yz Excited state (iii) d x 2 y 2 d x 2 d x 2 y 2 d x 2 Energy V 3+ uncomplexed Adding ligands Absorbing light d xy d xz d yz Ground state d xy d xz d yz Excited state -1 mark for every mistake. Maximum 6 marks. b) (i) No electrons in the 3d orbitals No electrons available for promotion (ii) All 3 d orbitals are full No empty higher level orbital for an electron to be promoted to

19 QUESTINSHEET 19 VANADIUM CHEMISTRY I a) 3d 4s 4p V [Ar] V 3+ [Ar] b) xidation Number Formula Colour Name +2 [V ] 2+ (Violet) (Vanadium(II)) +3 ([V ] 3+ ) Green (Vanadium(III)) +4 V 2+ (aq) Blue xovanadium(iv) +5 V 2+ (aq) range / yellow Dioxovanadium(V) c) range / yellow green blue green violet / lavender

20 QUESTINSHEET 20 VANADIUM CHEMISTRY II a) Shape ctahedral Types of bonding Covalent (within the ligand) and dative covalent / coordinate (between central metal and ligand) b) (i) Prediction Acidic Equation [V ] 3+ + ¾ [V(H) ) 5 ] 2+ + H 3 + (ii) Identity Vanadium(III) hydroxide / V(H) 3 / [V(H) 3 ) 3 ] Equation [V ] H - [V(H) 3 ) 3 ] + 3 c) (i) V 2+ (aq) + 2H + (aq) + e - V 2+ (aq) + (l) (2) (ii) S 3 2- (aq) + (l) S 4 2- (aq) + 2H + (aq) + 2e - (2) (iii) 2V 2+ (aq) + S 3 2- (aq) + 2H + (aq) 2V 2+ (aq) + S 4 2- (aq) + (l) (2) (iv) KMn 4 / K 2 Cr 2 7 / any other oxidising agent with Eê > V In the above equations, award for formulae and for balance. Examiners may accept equations without state symbols.

21 QUESTINSHEET 21 CHRMIUM CHEMISTRY I a) Equation [Cr ] 3+ + ¾ [Cr(H) ) 5 ] 2+ + H 3 + Explanation The solution contains [Cr ] 3+ ions which are purple / violet / blue and [Cr(H) ) 5 ] 2+ ions which are green b) bservation Green / grey-green (½) precipitate (½) which dissolves / is soluble in excess NaH(aq) to give a green (½) solution (½) Equations [Cr ] H - [Cr(H) 3 ) 3 ] + 3 [Cr(H) 3 ) 3 ] + H - [Cr(H) 4 ) 2 ] - + Accept equations for the formation of [Cr(H) 5 )] 2- or [Cr(H) 6 ] 3- Examiners may require state symbols of complexes, e.g. [Cr(H) 4 ) 2 ] - (aq) c) bservation From green / blue green to blue Half-equation [Cr ] 3+ + e - [Cr ] 2+ d) (i) Chromate(VI) ion r Cr 3+ (aq) + e - Cr 2+ (aq) (ii) Name Dichromate(VI) ion Equation 2 Cr 4 2- (aq) + 2H + (aq) Cr (aq) + (l) (2) Award for formulae and for balance. Examiners may accept an equation without state symbols.

22 QUESTINSHEET 22 CHRMIUM CHEMISTRY II a) Cr m/100g n 19.5/ / /18 = ratio empirical formula = Cr 3 b) X = [Cr ] 3+ Hexaaquachromium(III) ion Y = [Cr 2 ) 4 ] + Tetraaquadichlorochromium(III) ion c) The cations have different ligands attached to them causing different degrees of splitting of energy levels of d orbitals d) In Y, the chloride ions / chlorine atoms can be close to each other (cis isomer) or across the structure from each other (trans isomer) III Cr cis + III Cr + trans e) (i) [Cr ) 5 ] 2+ ( - ) 2 Ionic charges are not essential (ii) Two

23 QUESTINSHEET 23 CBALT CHEMISTRY I a) Transition element An element which forms one or more stable ions with incompletely filled d-subshells Example Co 2+ [Ar] 3d 7 / Co 3+ [Ar] 3d 6 Cationic complex Species with an overall +ve charge formed by coordination of ligands to a central cation Example [Co ] 2+ / [Co( ) 6 ] 2+ / [Co( ) 6 ] 3+ Anionic complex Species with an overall ve charge formed by coordination of ligands to a central cation Example [Co 4 ] 2- / [Co(H) 4 ] 2- b) II Co II Co c) Type of bonding Coordinate / dative covalent Feature Lone pair of electrons d) (i) Blue (½) precipitate (½) which dissolves in / is soluble in excess conc. (aq) to give a pale brown / red-brown (½) solution (½) (ii) Replacement / substitution of one type of ligand by another [Co ] [Co( ) 6 ] e) bservation Solution becomes dark brown Explanation xidation of Co II to Co III / formation of [Co( ) 6 ] 3+

QUESTIONSHEETS INORGANIC CHEMISTRY REACTIONS OF PERIOD 3 ELEMENTS WITH WATER REACTIONS OF PERIOD 3 ELEMENTS WITH OXYGEN

QUESTIONSHEETS INORGANIC CHEMISTRY REACTIONS OF PERIOD 3 ELEMENTS WITH WATER REACTIONS OF PERIOD 3 ELEMENTS WITH OXYGEN CHEMISTRY QUESTIONSHEETS A2 Level A2 TOPIC 21 INORGANIC CHEMISTRY Questionsheet 1 Questionsheet 2 Questionsheet 3 Questionsheet 4 Questionsheet 5 Questionsheet 6 Questionsheet 7 Questionsheet 8 Questionsheet