Acids n bases


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Acids n bases

  1. 1. Ethanoic acid (found in vinegar)  CH₃COOH  CH₃COO¯ (aq)  H⁺ (aq)Hydrochloric acid  HCl  Cl¯ (aq)  H⁺ (aq)Nitric acid  HNO₃  NO₃¯ (aq)  H⁺ (aq)Sulfuric acid  H₂SO₄  SO₄²¯ (aq)  H⁺(aq)Metal + acid -> salt + hydrogen - Unreactive metal (Copper & Silver) add to dilute acids -> no reaction - Concentrated nitric acid + metal (Eg. Copper) -> no hydrogen produced, only nitrate (salt) & water & nitrogen gas - Lead DO NOT react with dilute HCl & dilute Sulfuric acid  Layer of lead(II)chloride / lead(II)sulfate formed from initial reaction between lead & dilute acid  layer not soluble in water, quickly form coating around metal  coating protect metal from further attack from acidCarbonate + acid -> salt + H₂O + CO₂Metal oxide / hydroxide + acid -> salt + water (react same way)Acid UsesSulfuric - make detergent - make fertilizers - found in car batteriesEthanoic (in vinegar) - to preserve food - In making adhesives (sticky) Eg. glueHydrochloric (HCL) - in leather processing - for cleaning metals
  2. 2. Bases are any METAL OXIDE / METAL HYDROXIDE. - contain either oxide ions ( O²¯ ) / hydroxide ions (OH¯) - reacts with acid give salt & water onlyBase + acid -> salt & water - oxide / hydroxide ions from bases react with hydrogen ions from acid form waterAlkali is base that is soluble in water.All alkalis produce hydroxide ions when dissolved in water.When ammonia gas dissolve in water, ammonium ions & hydroxide ions are formed.  Ammonia + water -> ammonium ion + hydroxide ionAlkali + acid -> salt & water (neutralization)  hydrogen ions from acid + hydroxide ions from alkali react form waterAlkali heated with ammonium salt give off ammonia gas.  alkali + ammonium salt -> ammonia (alkali, pungent smell) + salt + H₂OAlkalis react with solution of 1 metal salt to give metal hydroxide + another metal salt  alkali +salt (metal a ) -> metal hydroxide(appears as precipitate if insoluble in water) + salt (metal b)Uses of bases & alkalisAmmonia solution - in window cleaning solutions - in fertilizersCalcium oxide - in neutralizing acidic soil - to make iron, concrete & cementMagnesium hydroxide - in toothpaste to neutralize acid on teeth - in antacids, relieve indigestionSodium hydroxide - in making soaps & detergent - in industrial-cleaning detergents
  3. 3. Concentration can be changed but strength cannot be changed. Concentration – how much a substance is dissolved in 1 dm³ of the solution? Strength – how easily acid / alkali dissociates when dissolved in water  strong acid dissociate easily (HCL)  Weak acid does not fully dissociate (Ethanoic) – much lower concentration of hydrogen ions in solution HCL strong acid no matter diluted / concentrated Ethanoic weak acid no matter diluted / concentrated PH value - calculated by no. of hydrogen/ hydroxide ions present in solution - acids with smaller value -> higher concentration of hydrogen ions - alkalis with bigger value -> higher concentration of hydroxide ions Soil PH - plants grow best in neutral / slightly acidic soil - plants do not grow when soil too acidic  happens when too much fertilizers added / acid rain - chemicals added to soil to raise PH  soil too acidic, treated with base : quicklime (calcium oxide) or slaked lime (calcium hydroxide)  known as “liming” the soil  but adding too much base will make soil too alkaline and unsuitable for plant growthIndicator Colour in acidic solution pH range which indicator Colour in alkaline changes colour solutionMethyl Orange Red 3-5 YellowScreened Methyl Violet 3-5 GreenOrangeLitmus Red 5-8 BlueBromothymol blue Yellow 6-8 BluePhenolphthalein Colorless 8-10 Pink
  4. 4. Oxides - many acids & alkalis form by dissolving oxides in water - compound of oxygen & another element - 4 types  amphoteric oxides can behave as both basic / acidic oxide Eg. Zinc oxide can react with both acids or bases to form salt and water formed only  neutral oxides show neither basic / acidic properties Eg. Water, Nitric oxide, carbon monoxide  acidic oxides (non-metals) may dissolve in water form acids Carbon dioxide -> carbonic acid Sulfur trioxide -> sulfuric acid Phosphorous (V) oxide -> phosphorous acid does not react with acids react with alkalis to form salt & waterExample: Silicon (IV) oxide solid at room temperature does not dissolve in water react with sodium hydroxide form sodium silicate (salt)  basic oxides (metals) mostly insoluble in water few oxide dissolve readily in water (called alkalis) (Eg. sodium oxide & potassium oxide) PAGE 186 DIAGRAMS!!!
  5. 5. Sulfur dioxide - acidic oxide - important for manufacture of sulfuric acid - Properties & uses1. as bleaching agent decolorize colored compounds, cause them to turn pale/ white SD bleach colour compounds by removing oxygen from them Substance like SD that remove oxygen from other substances -> called reducing agent Eg. Wood pulp to paper  Wood pulp colored due to dyes containing oxygen2. as food preservative SD poisonous to all organisms (esp. bacteria) In food industry, SD added to food in small prevents growth of mould & bacteria. Minute amt. sufficient to kill bacteria not humans but still poisonous so must strictly control amt. addedSulfuric acid - one of most widely used acids - cheapest and most readily available strong acid - Properties & uses of sulfuric acid1. Manufacture fertilizers (Eg. Ammonium sulfate, superphosphate) most important use A. S. -> salt formed when sulfuric acid reacted with alkali ammonia Super. -> manufactured by reacting raw material calcium phosphate Ca₃(PO₄)₂with concentrated sulfuric acid (combi. of 2 calcium salts)2. Manufacture detergents3. Battery acid in cars dilute s. acid used in batteries for cars lead & lead(IV) plates fitted in batteries when s. acid, lead & lead(IV) plates react, electrical energy produced -> starts car engine4. Used for making synthetic fibers & making paint & pigmentsSEE PAGE 190 CONCEPT MAP!!!