2024 Chemistry

• characteristics of catalyst


  increases reaction rates, not yield

  not used up in reaction

  selective -> only catalyse certain reactions

  impurities can poison them

  physical appearance may change but they remain chemically the same

  they provide an alternative pathway with a lower activation energy for the reaction
• common catalysts


  iron -> manufacture of ammonia in haber process

  aluminium oxide / silicon dioxide -> cracking of hydrocarbons

  nickel -> manufacture of margarine from vegetable oils

  platinum, palladium, rhodium -> catalytic converters
• biological catalysts are known as enzymes
• enzyme characteristics


  made of proteins

  temperature-sensitive -> operate best at body temperature. below temp -> enzymes are dormant, can be denatured, reducing catalytic activity. higher temp -> enzymes denatured, unable to catalyse reactions

  pH-sensitive -> operature best in optimal pH range which varies greatly. mostly inactive above/ below range

  specific catalytic action -> living cells contain many different types of enzymes, each catalyses a specific reaction
• applications of catalysts


  enzymes found in bacteria -> speed up manufacture of cheese, yoghurt, bread

  enzymes in laundry detergents -> break down oil/other stains that would otherwise require high heat / strong temperatures