CH9.3-5

CH9.3-5

1. Neutralization

   • acid+alkali==>salt+water
     • sodium hydroxide + hydrochloric acid ==> sodium chloride+water
     • potassium hydroxide+nitric acid ==> potassium nitrate+water
     • sodium hydroxide+ sulphuric acid ==> sodium sulphate+water
   • The mass of reactants and products is conserved in neutralization
   • applications of neutralization
     • brushing teeth with toothpaste
       • the bacteria in our mouth change sugars into acids, the alkali in toothpaste helps neutralize the acids
     • Treating stomachache with antacid
       • too much acid in our stomachs would irritate the stomach wall. The alkali in the antacid would neutralize the acid
     • regulating soil pH
       • Some crops have a range of pH that they are the most suitable to grow in. To ensure that the crops could grow, lime is added to the soil to neutralize the acids
     • Treating insect stings
       • Wasp stings are alkaline, vinegar is used to help neutralize it
       • Ant bites are acidic, baking soda is used to help neutralize it.
     • Treating chemical waste
       • Factories may release chemical waste with acids or alkalis and it will harm marine life. Acids or Alkalis would be put into the watse before it is discharged to netrualize it.

2. Corrosive Nature of acids-- dilute acids react with some metals and produce hydrogen. Then, the metals decrease in size.

   • metal+acid==> salt+ hydrogen
     • zinc+ hydrochloric acid ==> zinc chloride + hydrogen
     • iron+sulphric acid==> iron sulphate +hydrogen
   • carbonate+acid==>salt+water+carbon dioxide
     • calcium carbonate+ hydrochloric acid==> calcium chloride+water+carbon dioxide
     • magnesium carbonate+ sulphric acid==> magnesium sulphate+water+carbon dioxide

3. Acid Rain

   • Causes
     • Burning of fossil fuels , vehicles and factories releases air pollutants such as sulphur dioxide and nitrogen oxides
     • The sulphur dioxide and nitrogen oxides react with the oxygen and water, they form sulphiric acid and nitric acid
     • the gases make rain water more acidic, making acid rain
   • effects of acid rain
     • corroding metals and building materials
     • killing living this in water
     • damaging plants

4. potential hazards in handling acids and alkalis

   • Concentrated acids and alkali are ever corrosive. It can cause serious damage to skin and flesh
   • both acid and alkali are used in cleaning products, if some are mixed, toxic products may form. Heat may also be released in the process
   • rules to follow when using cleaning products
     • read the safety instructions on the containers carefully
     • keep the room well-ventilated
     • wear gloves, a mask and protective clothing
     • wash your hands thoroughly after using the products