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

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1 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 9 Questionsheet 10 Questionsheet 11 Questionsheet 12 Questionsheet 13 Questionsheet 14 Questionsheet 15 Questionsheet 16 Questionsheet 17 Questionsheet 18 Questionsheet 19 Questionsheet 20 Questionsheet 21 Questionsheet 22 Questionsheet 23 REACTIONS OF PERIOD 3 ELEMENTS WITH WATER REACTIONS OF PERIOD 3 ELEMENTS WITH OXYGEN STRUCTURE AND BONDING OF PERIOD 3 OXIDES PERIOD 3 OXIDES WITH WATER ACID - BASE CHARACTER OF PERIOD 3 OXIDES STABILITY OF GROUP 4 OXIDATION STATES HYDROLYSIS OF GROUP 4 CHLORIDES DEFINITIONS AND ELECTRONIC CONFIGURATIONS BONDING IN COMPLEX IONS COLOUR OF COMPLEX IONS ISOMERISM LIGAND EXCHANGE REACTIONS DEPROTONATION THEORY REACTIONS OF CATIONS WITH OH - AND NH 3 OXIDATION STATES COLORIMETRY LIGAND EXCHANGE AND STABILITY CONSTANTS d-orbital SPLITTING AND LIGHT ABSORPTION VANADIUM CHEMISTRY I VANADIUM CHEMISTRY II CHROMIUM CHEMISTRY I CHROMIUM CHEMISTRY II COBALT CHEMISTRY I 10 marks 12 marks 16 marks 17 marks 14 marks 18 marks 14 marks 19 marks 17 marks 12 marks 19 marks 13 marks 18 marks 18 marks 8 marks 5 marks 20 marks 10 marks 15 marks 14 marks 15 marks 15 marks 21 marks Curriculum Press Bank House 105 King Street Wellington Shropshire TF1 1NU

2 TOPIC 21 Questionsheet 1 REACTIONS OF PERIOD 3 ELEMENTS WITH WATER a) (i) Describe what is observed when sodium is added to a beaker of cold water.... [3] Quality of language [1] Write a balanced chemical equation for the reaction. (iii) Estimate the ph of the resulting solution. (iv) What type of chemical reaction occurs? b) (i) Why will magnesium and aluminium not react with cold water? Suggest how the conditions could be changed so that magnesium or aluminium would react in a similar way. 10

3 TOPIC 21 Questionsheet 2 REACTIONS OF PERIOD 3 ELEMENTS WITH OXYGEN a) Complete the following table for the elements of Period 3. Na Mg Al Si P S Cl Reaction conditions Formula of oxide (or lower oxide) [6] b) Write the fully balanced equation for the reaction of the elements with oxygen. (i) Na... [1] Mg... [1] (iii) Al... [1] (iv) Si... [1] (v) P... [1] (vi) S... [1] 12

4 TOPIC 21 Questionsheet 3 STRUCTURE AND BONDING OF PERIOD 3 OXIDES a) State the nature of the bonding in the oxides of Period 3 elements and the type of structure by completing the following table. Bonding Na 2 O MgO Al 2 O 3 SiO 2 P 4 O 10 SO 2 Cl 2 O Structure [5] b) On the basis of your answers to a), describe and explain how the melting points of these oxides vary across the period.... [8] (c) Why is magnesium oxide used in the manufacture of firebricks for lining high temperature furnaces, rather than calcium oxide?... [3] 16

5 TOPIC 21 Questionsheet 4 PERIOD 3 OXIDES WITH WATER a) On progressing from left to right across a period of the Periodic Table, what outstanding changes are observed in the behaviour of oxides with water? You should refer to three oxides of elements in either Period 2 (Li F) or Period 3 (Na Cl), and illustrate your answer by chemical equations.... [8] b) When a non-metallic element forms more than one oxide, how do these oxides compare in their acidic character? Refer in your answer to the oxides of carbon and phosphorus, write chemical equations for their reactions (if any) with water, and give the approximate ph values of the resulting solutions.... [9] 17

6 TOPIC 21 Questionsheet 5 ACID - BASE CHARACTER OF PERIOD 3 OXIDES a) Complete the following table to show the acid-base character of the oxides of elements in Period 3 of the Periodic Table. Oxide Na 2 O MgO Al 2 O 3 SiO 2 P 4 O 6 P 4 O 10 SO 2 SO 3 Acid - base character Cl 2 O ClO 2 Cl 2 O 7 b) For the oxides of magnesium and aluminium, and one oxide of sulfur, write balanced chemical equations to illustrate the acid-base character you have described in a).... [4] c) Write ionic equations, and apply the Bronsted-lowry theory or G.N.Lewis theory (or both), to explain the difference in acid-base behaviour between magnesium oxide and the oxide of sulfur you have selected in b).... [6] [4] 14

7 TOPIC 21 Questionsheet 6 STABILITY OF GROUP 4 OXIDATION STATES a) (i) State the oxidation states which are exhibited by the elements of Group 4. Tin occurs naturally as cassiterite, SnO 2. Lead occurs as galena, PbS, and cerussite, PbCO 3. What does this information suggest is: the more stable oxidation state of tin?... [1] the more stable oxidation state of lead?... [1] b) (i) Predict whether each of the following compounds could be expected to behave as an oxidising agent, reducing agent or neither. SnCl 2... [1] PbCl 2... [1] SnO 2... [1] PbO 2... [1] For each compound which you have described as an oxidising agent or reducing agent, give one example of the compound behaving as such. (Balanced equations are not required, but you must indicate both reactants and products.)... [4] c) Explain clearly why, on descending Group 4, one of the oxidation states mentioned in a) (i) increases in stability, while the other decreases.... [6] 18

8 TOPIC 21 Questionsheet 7 HYDROLYSIS OF GROUP 4 CHLORIDES a) (i) Write an equation for the reaction of silicon(iv) chloride with water at room temperature and outline the mechanism of the reaction. Equation... [1] Mechanism Explain why CCl 4 does not react in this way. b) (i) Lead(II) chloride is largely unaffected by cold water, but tin(ii) chloride behaves very differently. Describe what is observed when tin(ii) chloride is dissolved in water, write an equation for the reaction that occurs, and explain how this reaction can be prevented. Observation... [1] Equation... [1] Prevention [2] How do you account for the difference in behaviour of lead(ii) chloride and tin(ii) chloride with water?... [3] [4] 14

9 TOPIC 21 Questionsheet 8 DEFINITIONS AND ELECTRONIC CONFIGURATIONS a) Explain the difference between the terms d-block element and transition element. b) State, giving a reason in each case, whether or not scandium is: (i) a d-block element. a transition element. c) (i) Give the electron configuration of the following: 3d 4s Cu [Ar] 4p Cu 2+ Cr Cr 3+ [Ar] [Ar] [Ar] [4] In what way is the electron configuration of both copper and chromium unusual compared with the other first row of transition elements? Suggest why this occurs. Unusual feature [2] Reason for copper [2] Reason for chromium [2] d) (i) Name two stable cations having the following electronic configuration: 3d 4s 4p [Ar] What feature makes this electronic configuration stable? 19

10 TOPIC 21 Questionsheet 9 BONDING IN COMPLEX IONS a) (i) What is meant by the term ligand? Explain what is meant by the terms complex cation and complex anion and give an example of each. Complex cation [2] Example... [1] Complex anion [2] Example... [1] b) The hydrated chromium(iii) ion, Cr 3+ (aq), is a cationic complex. (i) State the shape of this ion and draw its structure [3] What type of bonding exists between the ligands and the chromium(iii) ion? (iii) Which structural feature of a water molecule and which structural feature of a chromium cation permit this bonding to occur? (iv) Draw appropriate arrows in the following boxes to represent orbital occupation in the hydrated chromium(iii) ion. Label the diagram so as to distinguish between electrons possessed by the simple Cr 3+ ion and those originating from the ligands. Cr 3+ [Ar] 3d 4s 4p [3] 17

11 TOPIC 21 Questionsheet 10 COLOUR OF COMPLEX IONS a) Complete the following table: ION Cr 3+ (aq) Mn 2+ (aq) Fe 2+ (aq) Fe 3+ (aq) Cu 2+ (aq) COLOUR b) (i) Give an example to show how, for a given metal in a and a given oxidation state, colour changes as the ligands are changed. c) (i) Draw the following electron configurations: [5] 3d 4s 4p Ti 4+ [Ar] Cu + [Ar] Zn 2+ [Ar] Ti 2+ [Ar] [4] Which of the above ions is/are coloured? (iii) Explain the choice you made in c).... [4] 12

12 TOPIC 21 Questionsheet 11 ISOMERISM a) [Co(NH 3 ) 5 Br]SO 4 (compound A) and [Co(NH 3 ) 5 SO 4 ]Br (compound B) are isomeric compounds. Suggest two simple tests which could be carried out in test tubes to distinguish between them. Test 1 Reagent... [1] Observation with compound A... [1] Observation with compound B... [1] Test 2 Reagent... [1] Observation with compound A... [1] Observation with compound B... [1] b) There are five compounds of platinum(iv) chloride and ammonia, each containing a different octahedral complex ion. Details are given below. Compound Molecular formula No. of chloride ions per mole A PtCl 4.6NH 3 4 B PtCl 4.5NH 3 3 C PtCl 4.4NH 3 2 D PtCl 4.3NH 3 1 E PtCl 4.2NH 3 0 (i) Draw the complex ions in compounds A, B, C and D. [4] Outline a simple experimental method to distinguish between compounds A, B, C and D.... [3] TOTAL (Continued...) /

13 TOPIC 21 Questionsheet 11 Continued ISOMERISM c) (i) The square planar compound [NiCl 2 (NH 3 ) 2 ] can occur as two geometric isomers. Draw their structures and label each as cis or trans. [3] The octahedral complex cation [CoCl 2 (NH 3 ) 4 ] + can also occur as two geometric isomers. Again, draw their structures and label each as cis or trans. [3] 19

14 TOPIC 21 Questionsheet 12 LIGAND EXCHANGE REACTIONS a) Define the term ligand exchange reaction, as applied to the hydrated cations of transition elements, and give two reasons why such reactions may occur. Definition... Reason 1... [1] Reason 2... [1] Quality of language [1] b) Starting from [Cu(H 2 O) 6 ] 2+, give examples of the following types of reaction. In each case write an ionic equation, describe the colour change that would be observed, and state the shape of the resulting complex ion. (i) Ligand exchange reaction with no change in coordination number Ionic equation... [1] Colour change... [1] Shape of resulting complex ion... [1] Ligand exchange reaction accompanied by a change in coordination number Ionic equation... [1] Colour change... [1] Shape of resulting complex ion... [1] c) Suggest a reason why there is a change in coordination number in some ligand exchange reactions but not in others. 13

15 TOPIC 21 Questionsheet 13 DEPROTONATION THEORY a) (i) When iron(iii) chloride is dissolved in pure water, how does the ph change? Give reasons for any ph change, and support your answer with a balanced ionic equation. Reasons [3] Equation... [1] (iii) State the type of reaction occurring in a) and give the chemical functions of both the hydrated metal ions and the water molecules. Type of reaction... [1] Function of hydrated metal ions... [1] Function of water molecules... [1] b) On standing for several weeks, a solution of iron(iii) chloride may deposit a small amount of iron(iii) hydroxide. (i) Write ionic equations (following on from that in a) ) to represent the formation of iron(iii) hydroxide. If OH - ions (e.g. from NaOH(aq)) are introduced into iron(iii) chloride solution, iron(iii) hydroxide is precipitated copiously and immediately. How do you account for the difference? c) The ph value of a solution formed by dissolving copper(ii) sulfate in water differs from the ph of a solution of iron(iii) chloride, even when the molar concentrations of the hydrated cations are equal. (i) Predict whether the copper(ii) sulfate solution is acidic, neutral or basic, giving your reasoning. Also suggest, giving reasons, which solution has a ph value further from neutrality.... [5] 18

16 TOPIC 21 Questionsheet 14 REACTIONS OF CATIONS WITH OH - AND NH 3 a) Both NaOH(aq) and NH 3 (aq), when used in limited amounts, behave in the same way when added to aqueous solutions of transition element salts. (i) Why is this? Quote three examples from the first row of d-block elements to illustrate this statement, giving your expected observation and formula of the compound produced in each case. Example 1... Example 2... Example 3... [3] b) NaOH(aq) and NH 3 (aq) behave very differently from each other when they are added to aqueous solutions of transition element salts until they are eventually present in excess. Excess NaOH(aq) will dissolve some of the compounds produced at first, while excess NH 3 (aq) will dissolve others. Illustrate the differences in observations and underlying chemistry by completing the following table. Excess dilute NaOH(aq) Excess NH 3 (aq) Example of a compound which will dissolve Reason for dissolving Type of reaction occurring Observation Formula of the ion produced c) (i) Name two compounds of p-block elements, produced by the action of NaOH(aq) on salt solutions, which also dissolve when the reagent is present in excess. [10] Give the formulae of the ions produced in these reactions.... [2] 18

17 TOPIC 21 Questionsheet 15 OXIDATION STATES a) Give the oxidation number of the transition element in each of the following chemical species: (i) CrO MnO (iii) Fe 2 Cl 6... (iv) VO (v) VO (vi) [CrCl(H 2 O) 5 ] (vii) [PtCl(NH 3 ) 5 ] (viii) [Co(NH 3 ) 4 Cl 2 ] (ix) Na 2 FeO 4... (x) K 2 CuF 4... [5] b) Why do transition elements show a variety of oxidation states in their chemistry?... [3] 8

18 TOPIC 21 Questionsheet 16 COLORIMETRY a) meter reading 0 cm cm cm 3 0 cm 3 volume of 0.1 M CuSO 4 (aq) volume of 0.1 M NH 3 (aq) The above graph shows the results obtained when aqueous copper(ii) sulfate and aqueous ammonia are mixed together in different proportions in the presence of ammonium sulfate. A complex is formed between ammonia and the copper(ii) ion, which has a different and much more intense colour than [Cu(H 2 O) 6 ] 2+. (i) What volumes of 0.1 mol dm -3 CuSO 4 (aq) and 0.1 mol dm -3 NH 3 (aq), when mixed together, give the highest concentration of the complex? Volume of 0.1 mol dm -3 CuSO 4 (aq)... Volume of 0.1 mol dm -3 NH 3 (aq)... [1] Calculate the mole ratio of Cu 2+ : NH 3 in the complex.... [3] (iii) Write down the formula of the complex. 5

19 TOPIC 21 Questionsheet 17 LIGAND EXCHANGE AND STABILITY CONSTANTS (a) Aqueous nickel(ii) sulfate contains the [Ni(H 2 O) 6 ] 2+ ion. (i) The green nickel(ii) sulfate turned blue when treated with aqueous ammonia. This blue solution when treated with aqueous sodium cyanide turns yellow, but this yellow colour is unaffected by the addition of excess aqueous ammonia. Explain these observations, stating what is formed and why, but formulae of any complex ions formed is not required.... [6] Quality of language [1] When aqueous ethane-1,2-diamine was added to the blue solution described in part (i) (ie aqueous nickel sulfate and aqueous ammonia), it turned mauve. However, aqueous ethane-1,2-diamine had no effect on the yellow solution described in part (i). Explain these observations, stating what is formed and why, but formulae of any complex ions formed is not required.... [4] TOTAL (Continued...) /

20 TOPIC 21 Questionsheet 17 Continued LIGAND EXCHANGE AND STABILITY CONSTANTS (a) Using Stability Constants Data (Note: en = ethane-1, 2-diamine) Complex ion Stability Complex ion Stability constant (lgk) constant (lgk) [Cu(NH 3 ) 2 ] + 11 [Co(NH 3 ) 6 ] 2+ 5 [Cu(CN) 4 ] 3-27 [Co(NH 3 ) 6 ] [Cu(NH 3 ) 4 (H 2 O) 2 ] [Co(CN) 6 ] [Cu(en) 2 (H 2 O) 2 ] [Co(EDTA)] [Cu(EDTA)] 2-19 [Co(EDTA) - 36 (i) The complex ion [Cu(NH 2 CH 2 CH 2 NH 2 ) 2 (H 2 O) 2 ] 2+ contains the ethane-1,2-diamine ligand, would you expect it to be displaced by EDTA? Use the data to explain your answer. The ion [Cu(H 2 O) 6 ] 2+ reacts with cyanide ions to give the complex ion [Cu(CN) 4 ] 3-. Would you expect the cyanide ions to be replaced by ammonia? Use the data to explain your answer. (iii) 0.02 moles of [Co(H 2 O) 6 ] 3+ was treated with 0.12 moles of potassium cyanide and 0.12 moles of ammonia. What would be the formula of the complex ion? Show how you get the answer.... [3] (iv) 0.02 moles of [Co(H 2 O) 6 ] 3+ and 0.02 moles of [Co(H 2 O) 6 ] 2+ were mixed with 0.12 moles of ammonia. What would be the formula of the complex ion?... [3] 20

21 TOPIC 21 Questionsheet 18 d-orbital SPLITTING AND LIGHT ABSORPTION a) Complete the diagrams below (i) Write down the electronic structure of Cu 2+ in an octahedral complex and hence complete the diagram 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 Write down the electronic structure of Fe 3+ in an octahedral complex and hence complete the diagram 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) Write down the electronic structure of V 3+ in an octahedral complex and hence complete the diagram 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 [6] b) Explain why the following ions form white compounds (i) Sc [2] Zn [2] 10

22 TOPIC 21 Questionsheet 19 VANADIUM CHEMISTRY I a) Complete the following table to give the electronic structure of V and V 3+. 3d 4s 4p V [Ar] V 3+ [Ar] [2] b) Complete the following table by giving the colours and names of the aqueous cations of vanadium. Oxidation Number Formula Colour Name +2 Violet Vanadium(II) +3 [V(H 2 O) 6 ] 3+ Vanadium(III) [8] c) What colour changes would you expect to see when a sample of ammonium vanadate(v) is dissolved in warm aqueous sulfuric acid and zinc is added?... [5] 15

23 TOPIC 21 Questionsheet 20 VANADIUM CHEMISTRY II a) The complex ion [V(H 2 O) 6 ] 3+ is present in aqueous solutions of vanadium(iii). State its shape and describe the types of bonding in this ion. Shape... [1] Types of bonding... b) (i) Predict whether a solution containing [V(H 2 O) 6 ] 3+ would be acidic, basic or neutral. Write an ionic equation to support your prediction. Prediction... [1] Equation... [1] When a solution containing [V(H 2 O) 6 ] 3+ is treated with NaOH(aq) a green precipitate is obtained. Suggest the identity of this precipitate and write an ionic equation for its formation. Identity... [1] Equation... [1] c) VO 2+ (aq) can be reduced using an acidic aqueous solution containing sulfite ions. (i) Write an ionic half-equation for the reduction of VO 2+ (aq) in acidic solution to VO 2+ (aq).... [2] Write an ionic half-equation for the oxidation of sulfite ions in aqueous acidic solution to form sulfate ions. (iii) Using your answers from parts (i) and, deduce an equation for the reduction of VO 2+ (aq) in acidic solution to VO 2+ (aq) by sulfite ions. (iv) Suggest a reagent which could be expected to convert a solution of VO 2+ (aq) ions to VO 2+ (aq) ions. 14

24 TOPIC 21 Questionsheet 21 CHROMIUM CHEMISTRY I a) When the purple salt, chromium(iii) nitrate-9-water, is dissolved in water, a blue-green solution A is obtained. With the help of an ionic equation, explain the colour change which occurs on dissolving. Equation... [1] Explanation... b) Aqueous sodium hydroxide was added dropwise to a sample of A, followed by an excess of aqueous sodium hydroxide to form solution B. What observations were made? Write ionic equations to describe the reactions occurring. Observations [3] Equations... c) Zinc metal and aqueous hydrochloric acid were added to a sample of A. What colour change would be seen to occur? Write an ionic half-equation to describe the reaction occurring to A. Observations... [2] Half-equation... [1] d) To B was added aqueous sodium hydroxide and aqueous hydrogen peroxide. The solution was boiled. The colour of the solution became yellow. Excess hydrogen peroxide was then removed and the solution was acidified. Finally, an orange colour formed. (i) Name the chemical species responsible for the yellow colour. Name the chemical species responsible for the orange colour and write a balanced ionic equation for its formation from the yellow species. Name... [1] Equation [2] 15

25 TOPIC 21 Questionsheet 22 CHROMIUM CHEMISTRY II When an aqueous solution of chromium(iii) chloride is evaporated at room temperature, violet crystals are formed (compound X). When a hot aqueous solution of chromium(iii) chloride crystallises, pale green crystals (compound Y) are formed. When an excess of silver nitrate is added to 1 mole of either of these salts a white precipitate of silver chloride is formed. Compound X forms 3 moles of silver chloride and compound Y forms only 1 mole of silver chloride. Both compounds have the same composition by mass: 19.5% chromium, 40.1% chlorine and 40.4% water. a) Calculate the empirical formula of both these salts.... [3] b) Assuming that the empirical formulae are identical with the molecular formulae, what are the formulae and names of the complex cations present?... [4] c) Why do these compounds have different colours? d) One of these complex ions can exhibit geometric isomerism. Using sketches, explain how such isomerism can occur. e) (i) Give the formula of a third compound Z which is isomeric with compounds X and Y. [4] How many moles of silver chloride would you expect to be precipitated from 1 mole of compound Z on treatment with excess silver nitrate solution?... [1] 15

26 TOPIC 21 Questionsheet 23 COBALT CHEMISTRY I a) Explain the meaning of the terms transition element, cationic complex and anionic complex, and illustrate your answers with examples taken from the chemistry of cobalt. Transition element... Example... [1] Cationic complex... [2] Example... [1] Anionic complex... Example... [1] b) Sketch the structures of two complex ions of cobalt(ii), one of which has an octahedral shape and the other one a tetrahedral shape. c) State the type of bonding occurring between the central metal cation and a ligand. What structural feature must a ligand possess for this type of bonding to occur? Type of bonding... [1] Feature... [1] d) (i) Describe what you would observe if concentrated aqueous ammonia were added dropwise (until in excess) to an aqueous solution of cobalt(ii) nitrate.... [3] [2] Using your answer to d) (i), explain the meaning of the term ligand exchange reaction. Include in your explanation the chemical equation for the reaction involved.... [3] e) What would you observe if the solution resulting from d) (i) were allowed to stand in air, and how do you account for the change? Observation... [1] Explanation... [1] 21

(a) (i) Explain what is meant by the terms transition element, complex ion and ligand,

(a) (i) Explain what is meant by the terms transition element, complex ion and ligand, 1. This question looks at the chemistry of transition elements. (a) Explain what is meant by the terms transition element, complex ion and ligand, Discuss, with examples, equations and observations, the