1	Core & Ext. Metals II: Displacement Rxns & Stability of Compounds
2	Learning Objectives Concepts: Reactivity, displacement, reduction, metal, thermal decomposition, order of reactivity Skills Core: Deduce an order of reactivity from a given set of experimental results Extension: Describe the reactivity series as related to the tendency of a metal to form its positive ion, illustrated by its reaction, if any, with the aqueous ions, the oxides of the other listed metals Describe the action of heat on the hydroxides and nitrates of the listed metals Account for the apparent unreactivity of aluminum in terms of the oxide layer which adheres to the metal
3	Extension: Displacement (reactions) To displace: to kick something out and take its place.
4	Displacement The South Park Way Cartman, Stan, Kyle and Kenny are good friends…well most of the time…except when it comes to the question of who gets to play with piggy. Cook, of course tries to help settle any argument or console any kid. Piggy remains in a small pen waiting for one or more of the kids to come and play with it.
5	Displacement of Stan And today, Stan comes along to play with it.
6	Displacement of Stan And as you all know, Cartman gets what he wants!
7	Displacement of Stan
8	Displacement of Stan Who is the stronger (bully) -- CARTMAN or STAN ? WhAt happened to STAN and Why ?
9	Kyle’s Story The following day Kyle wakes up early and runs over to piggy and starts playing with it and having a grand ol’ time!
10	Displacement of Kyle Until Stan, having woken up a little late, gets around to Piggy’s sty to find Kyle spending some quality time with it.
11	Displacement of Kyle
12	Displacement of Kyle Who is the stronger (bully) -- Kyle or STAN ? WhAt happened to Kyle and Why ?
13	Kenny’s Story The following day, while Kenny was trying to get some one-one time with piggy…
14	Displacement of Kenny
15	Displacement of Kenny Who is the stronger (bully) -- Kenny or KYLE ? WhAt happened to Kenny and Why ?
16	Kenny’s Day? The following day, Kenny, remembering how he got displaced by Stan, woke up early so that he could cosy up to piggy.
17	Kenny’s Day? Cook had to come along and console Kenny!!
18	Displacement Who is the stronger (bully) -- Cartman or Kenny ? WhAt happened to Kenny and Why ? Who is the biggest bully of them all? What is the hierarchy of the bullies? Who would win the company of piggy if Kyle were to come along and find Cartman with piggy? Why? Who would win the company of piggy if Stan were to come along and find Kenny with piggy? Why?
19	Displacement: tendency of Metal to form ion When an Iron nail is placed in a solution of copper sulfate, a coating of copper forms on the surface of the nail and the solution changes from pale blue to colorless.
20	Displacement Reaction And just as Stan is a stronger bully then Kyle, and is able to kick him out to be with Piggy, so it is with iron and copper. Because iron (Fe) is a more reactive metal (it occurs higher up in the reactivity series), it is able to displace copper ions from the solution and take it’s place.
21	Displacement Reaction: Examples In a displacement reaction, a more reactive metal will displace a less reactive metal from a solution. What will happen if a piece of copper is placed in a beaker of calcium chloride solution?
22	Displacement Reactions In general when there is a displacement reaction the following reaction take place: Metal 1 + Metal 2 salt solution ¾® Metal 1 salt solution + Metal 2 You tested four metals again with solution of salts of the other three metals. Magnesium was able to displace all the other metals from their salt solution. Word equation: Magnesium + Zinc sulfate ¾® Magnesium sulfate + Zinc (Chemical) equation: Mg(s) + ZnSO_{4 (aq)}¾®MgSO_{4 (aq)} + Zn Ionic equation: Mg_(s) + Zn²⁺_(aq) ® Mg²⁺_(aq) + Zn_(s) You must be able to write equations for the rest of the displacement reactions you observed.
23	Displacement Reactions Zinc was able to displace all but magnesium. Zinc + Magnesium sulfate ¾® No reaction Zinc + Iron sulfate ¾® Zinc sulfate + Iron Zinc + Copper sulfate ¾® Zinc sulfate + Copper Iron was able to displace only copper. Iron + Magnesium sulfate ¾® No reaction Iron + Zinc sulfate ¾® No reaction Iron + Copper sulfate ¾® Iron sulfate + Copper
24	Displacement Reactions Copper was not able to displace any metals. Copper + Magnesium sulfate ¾® No reaction Copper + Zinc sulfate ¾® No reaction Copper + Iron sulfate ¾® No reaction The results of the displacement reaction test confirmed the order of the reactivity, namely: Magnesium, then Zinc, then Iron and Copper. Aluminum is more reactive than Zinc, Iron, and Copper but less reactive than Magnesium. The order with aluminum placed in the series is thus: Potassium, Sodium, Calcium, Magnesium, Aluminum, Zinc, Iron, and Copper.
25	Metal displacement from oxide The third type of reaction of which you observed was that between a metal and the oxide of another metal (the thermit reaction). This reaction was the spectacular reaction between aluminum and the oxide of iron. Aluminum + Iron oxide ¾® Aluminum oxide + Iron Al _(s) + Fe₂O_{3 (s)} ¾® Al₂O_{3 (s)} + Fe _(l) A more reactive metal will displace a less reactive metal from it’s oxide. Metal 1 + Metal 2 oxide ¾® Metal 1 oxide + Metal2 Exercise: Write at least 3 equations for a metal and oxide of another metal where there would be a displacement reaction if the conditions were right.
26	Position of hydrogen in the Series The position of hydrogen can be determined by performing displacement reactions between hydrogen gas and metal oxide. In general, where there is a reaction, the following take place: Hydrogen + Metal oxide ¾® metal + water Whether the reaction does occur (whether hydrogen is able to displace the metal from the oxide) depends on the relative reactivities of the metal and hydrogen. Though you might not be aware, you already know the relative reactivity of hydrogen compared to at least a few different metals. (This is based on metal acid reaction. Any ideas?) You were able to perform some displacement reactions between hydrogen and metal oxides.
27	Position of hydrogen in the Series What did you find out? Was hydrogen able to displace copper from it’s oxide? What about iron, zinc? You should have noted that hydrogen was able to displace only copper but not iron nor zinc. Hydrogen + copper oxide ¾® copper + water Hydrogen + iron oxide ¾® no reaction Hydrogen + zinc oxide ¾® no reaction Based on these results, hydrogen can be placed between iron and copper in the series.
28	Position of hydrogen in the Series Notice then that because hydrogen is more reactive than copper, it is able to displace copper from its oxide, and copper is NOT able to displace hydrogen from an acid. copper + hydrochloric acid (contains hydrogen) ¾® no reaction On the other hand, since hydrogen is less reaction than iron, it was not able to displace iron from its oxide, and consequently iron is able to displace hydrogen from an acid. iron + hydrochloric acid (contains hydrogen) ¾® iron chloride + hydrogen
29	Stability of Nitrates and Hydroxides
30	Stability of Nitrates and Hydroxides
31	Stability of Nitrates and Hydroxides Group 1 metal compounds are relatively stable—either they don’t decompose of if they do decompose to fewer products—because of their strong reactivity. In other words, the more reactive the metal, the stronger the metal ion holds on to the negative ion in the ionic lattice (stronger the bonds between the positive metal ion and the negative ions). Or state in another way, the more reactive the metal, greater the tendency for the metal to remain in the ionic form and therefore the more stable their compounds. This relative stability extends to other ionic compounds as well, such as carbonates, which when decompose, produce the oxide and carbon dioxide.
32	Metal reactivity series
33	Summary The more reactive the metal, the stronger the tendency for it to be in the ionic state. For instance, it will displace the ion of a less reactive metal from a salt solution converting it into an atom, while itself changing from the atomic state to an ionic state. It will also displace the ion of a less reactive metal from the oxide of the metal converting into an atom while itself changing from the atomic state to an ionic state (in the oxide into which it transforms). The more reactive the metal the more stable its compound to heat. If unstable, the hydroxide decomposes to the oxide and water. The nitrates either to nitrite and oxygen or oxide, nitrogen dioxide and oxygen. Carbonates to oxide and carbon dioxide.
34	Paper 3 Practice Questions 1. J05/3/6 (d) Predict the equations for the decomposition of the following aluminium compounds. (i) . . . . Al(OH)₃ ® . . . . . . . . . . . . . + . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [2] (ii) aluminium nitrate ® [2]
35	Paper 3 Practice Questions 2. N04/3/4. In the following list of ionic equations, the metals are in order of reactivity.
36	Paper 3 Practice Questions 3. N04/4/7. (a) (i) Write a symbol equation for the action of heat on zinc hydroxide. [2] (ii) Describe what happens when solid sodium hydroxide is heated strongly. [1] (b) What would be observed when copper(II) nitrate is heated? [3] 4. J03/3/4. Nitrogen dioxide, NO₂, is a dark brown gas. (a) Most metal nitrates decompose when heated to form the metal oxide, nitrogen dioxide and oxygen.
37	Paper 3 Practice Questions (i) Write a symbol equation for the decomposition of lead(II) nitrate. Pb(NO₃)₂ → ............... + ............... + ............................ [2] (ii) Potassium nitrate does not form nitrogen dioxide on heating. Write the word equation for its decomposition. [1] 5. N02/3/4. (d) Copper is an unreactive metal. Its compounds are easily reduced to the metal or decomposed to simpler compounds. Complete the following equations. (i) ...CuO + ............................ → ...Cu + ............................ (ii) Copper(II) hydroxide (Heat)→ ............................ + ............................
38	Paper 3 Practice Questions (iii) Cu(NO₃)₂ (heat) → ................................. + ............................ + ........................... [4] 6. J02/3/1. In 1886, the modern electrolytic process for the extraction of aluminium was discovered in the USA by C. Hall. (a) Before this discovery, the only method of extracting the metal was by displacement. (i) Name a metal that can displace aluminium from aluminium chloride. [1] (ii) Write a word equation for this displacement reaction. [1]
39	Paper 3 Practice Questions (iii) Complete the equation for the reaction. AlCl₃ + ....................... → ...................................... + ........................................ [2] 7. N01/3/4. (a) Zinc is made by reducing zinc oxide. In 1695 Homberg obtained zinc from calamine, zinc carbonate. At present zinc is extracted from the ore, zinc blende. (i) Suggest a way of changing calamine into zinc oxide. [1] (b) Zinc oxide is used to make aqueous zinc chloride. This can be used to preserve wood. Describe how this solution could be made. [3]
40	Paper 3 Practice Questions (d) Another use of zinc is galvanising. When the zinc layer is broken, the steel is exposed. Explain why the exposed steel does not rust. [3]
41	Paper 6 Practice Questions 1. J04/6/6. Copper oxide was reacted with hydrogen using the apparatus shown below.
42	Paper 6 Practice Questions (a) Indicate on the diagram with an arrow where the copper oxide is placed. [1] (b) The colour of the copper oxide would change from to [2] (c) What is the purpose of the ice? [2]