acids, bases and salts

• what’s an acid 


  A substance sometimes called a proton that produces hydrogen ions (H+) when dissolved in water
• what’s an alkali

  A substance that produces hydrogen ions (OH-) when dissolved in water
• whats a base

  a substance chemically opposite to an acid and neutralises acids
• what does ionise mean?


  to split molecules and release hydrogen ions
• product of acid + metal

  Salt + hydrogen
• relation between concentration, pH and strength of acids

  the higher the concentration of acid solution the stronger the acid and lower the pH
• characteristic of strong acids

  Fully dissociates in water, achieves maximum number of hydrogens, examples - hydrochloric sulphuric and nitric
• characteristics of weak acids

  Partially dissociates in water does not contain maximum number of hydrogen ions, examples - ethanol citric and carbonic
• difference between strong and weak acid in reactions

  The rate of reaction for stronger acid is faster due to more hydrogen released meaning reaction occurs faster
• what type of reaction is the reaction of acid with metals bases or carbonate?

  exothermic (heat energy released)
• Word symbol for hydrochloric acid

  HCL
• Word symbol for sulfuric acid

  H2SO4
• Word symbol for nitric acid

  HNO3
• Word symbol for ethanoic acid

  CH3COOH
• neutralisation


  The loss and gain of hydrogen atoms acids react with alkaline producing salt and water

  $acid +$$alkali -> salt +$$water$
• ionic equation for neutralisation


  $(H+) +$$(OH-) -> H2O$
• neutralisation reactions

  • Acid + base/alkaline = salt + water
  • Acid + Metal carbonate = salt + water + carbon dioxide
• definition of salt

  A substance produced by the reaction of an acid with a base
• how to name a salt (of two parts)

  1. comes from metal, base or carbonate
  2. Comes from the acid
• steps of neutralisation

  Metal or insoluble base added to gently heated dilute acid until access is made.

  Mixture is then filtered to obtain pure salt solution.

  Solution heated to evaporate leaving salt crystals
• Titration

  method use to prepare salts when produced when alkaline reacts with acid
• steps of titration

  1. fixed volume of alkaline into clinical flask adding in a few drops of indicator, slowly adding acid from a burette into indicator changes colour determining the endpoint
  2. repeat steps without indicator to allow it’s not contaminated
  3. evaporation
• titration calculation

  concentration = no. of moles / volume
• rules of titration calculation

  divide volume by 1000 to convert into DM3

  Number of moles = mass divided by MR
• insoluble salts


  do not dissolve in water, formed when two soluble salts react together in a precipitation reaction
• precipitate


  insoluble solid formed when two solutions react
• how to identify carbonate

  Add dilute acid if fizzing test for CO2 by bubbling in limewater if it turns cloudy CO2 is present meaning carbonate is present
• halides 


  chemical compounds that contain halogen ions such as chlorine, bromine and iodine, combined with a metal ion
• how do identify halides

  add dilute nitric acid and dilute silver nitrate to produce different coloured precipitate chloride turns white, bromide turns cream and iodide turns yellow
• how to identify sulfate


  add dilute hydrochloric acid and barium chloride solution if sulfate is present then white precipitate is produced
• identification of metal hydroxide precipitates (calcium, magnesium, and aluminium ions)

  add sodium hydroxide, creating white precipitate adding access sodium hydroxide, causes aluminium to redissolve, to identify calcium and magnesium must perform flame test
• flame test

  Lithium - crimson red

  Sodium - yellow

  Potassium - lilac

  Calcium - orange/ red

  Copper - green

  Magnesium - white
• stages of preparation of insoluble salts

  1. mixing
  2. filtration
  3. washing
  4. drying