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The purpose of this experiment is to study the effect of an oxidizing acid [concentrated sulphuric(VI) acid] and a non-oxidizing acid [ concentrated phosphoric(V) acid] on three solid potassium halides, namely potassium chloride, potassium bromide and pot

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Introduction

1. Title Reactions of solid halides 2. Aim The purpose of this experiment is to study the effect of an oxidizing acid [concentrated sulphuric(VI) acid] and a non-oxidizing acid [ concentrated phosphoric(V) acid] on three solid potassium halides, namely potassium chloride, potassium bromide and potassium iodide.. 3. Results & Calculations Table 1 Halide ion Action of conc. H2SO4(l) & MnO2 Product(s) Confirmatory test of product(s) Cl- Steamy fumes are formed Cl2 A yelllow colour is observed when adding hexane Br- Br2 A red colour is observed when adding hexane I- I2 A violet colour is observed when adding hexane Table 2 Halide ion Action of conc. H2SO4(l) Product(s) Confirmatory test of product(s) Cl- * Steamy fumes are formed * No green gas is evolved even on heating HCl * Dense white fumes are formed with aqueous ammonia * It turns blue litmus paper red but not bleached Br- * Steamy fumes are formed * A pungent smell is detected * A brown gas is evolved on warming HBr * White fumes are formed with aqueous ammonia SO2 * It turns orange dichromate(VI) ...read more.

Middle

The Br2 is then dried with anhydrous CaCl2. The bromine liquid is purified by distillation. NaBr + H2SO4 --> HBr + NaHSO4 MnO2 + 4H+ + 2Br- --> Mn2+ + 2H2O + Br2 For iodine, it is similar to Br2, using KI + conc. H2SO4. MnO2 is not required because I- is a strong reducing agent. The I2 collected is purified by sublimation. KI + H2SO4 --> HI + KHSO4 8HI + H2SO4 --> H2S + 4H2O + 4I2 Table 2: Concentrated sulphric (VI) acid is often said to be an oxidizing acid as it exhibits both oxidizing agent and acidic properties. On treatment with concentrated sulphric acid (VI) acid, chlorides give hydrogen chloride. However, bromides and iodides do not give hydrogen bromide and hydrogen iodide respectively when concentrated sulphuric (VI) acid is added to them. Instead, sulphur dioxide or hydrogen sulphide is formed. Bromides and iodide do not react in the same way with concentrated sulphuric (VI) acid as chlorides. It is because the hydrogen bromide and hydrogen iodide produced are oxidized by concentrated sulphuric (VI) ...read more.

Conclusion

+ 4H2O (l) Table 3: 3KCl(s) + H3PO4 (l)--> K3PO4(s) + 3HCl (g) 3KBr(s) + H3PO4 (l)--> K3PO4(s) + 3HBr (g) 3KI(s) + H3PO4 (l)--> K3PO4(s) + 3HI (g) 5.2 What is the relationship between H-X bond enthalpy and its tendency to undergo further oxidation? [X=Cl/Br/I] Electron affinity of halogens is the enthalpy change when one mole of electrons is added to one mole of halogen atoms or ions in the gaseous state. The electron affinity decreases from chlorine to iodine. The general decrease in electron affinity is due to the increases in atomic size and number of electrons shells down the group this leads to a decrease in effective charge. Therefore, the tendency of the nuclei of halogen atoms to attract additional electrons decreases. 5.3 State the function of manganese (IV) oxide added in experimental procedure (A). Manganese (IV) oxide is a strong oxidizing agent. When manganese (IV) oxide reacts with reducing agents, it is often reduced to manganese (II) ions 6. Conclusion The reducing ability of the halide ions increases as we go down the Group when react with an oxidizing acid. ...read more.

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