Acids and alkali

• Anything below 6 on the PH is acid
• Anything over 8 is an alkali
• 7 in the PH is neutral
• Ph probe is better than universal indicator because universal indicator only shows you the colour but doesnt tell you the exact PH whereas ph meter gives you exac PH value
• A term that describes a substance that attacks metal or skin is called corrosive
• A substance that isnt a alkali nor a acid is neutral
• Indicators are chemicals that change colour of an acid or alkali
• Litmus paper turns alkali blue and acids red
• Methyl orange turns alkali yellow and acid red
• phenolphthaelin turns alkali pink and acid colourless
• Common acids are sulfuric acid, hydrochloric acid, nitric acid
• The further your PH value is from 7 the more stronger acidity or alkanity it is
• When acids dissolve in water acids produce an excess of hydrogen ions which are H+ when they dissolve in water
• An ion is an atom that has gained or lost an electron
• Alkalis produce an excess of hydroxide ion OH- in water
• Polyatomic ions form when small groups of atoms held together by covalent bonds lose or gain electrons
• We have the charges of sulfur and nitrate and hydroxide

  No-3

  SO2-4

  OH-
• The higher the number of hydrogen ions in a certain volume the higher the concentration the higher the concentration is the more acidic or alkaline they are
• When breaking down an acid or alkali to their ions they need to have an overall charge of 0 so for example HCl is made up of H+ and Cl- they both have a charge of 0 because the -1 and +1 cancel each other out
• Neutral ions will have the same number of hydrogen ions and hydroxide ions
• Whenever you increase Ph the less acidic it become for example if HCL is added to pure water it will become more acidic because the concentration of H+ decreases causes hydrochloric acid to becomes less acidic
• Whenever you add a neutral solution to another neutral solution it would stay the same because they have the same amount of H+ ions and hydroxide ions
• Concentration how much of something there is in a volume of solution.
• On the ph scale each time you go down the scale the more larger the amount of H+ ions there are for example solution x has a ph of 2 and solution y has a ph of 4 solution x is 100x stronger than solution y
• A strong acid is one which fully dissociates(splits up into ions) with the solution
• Strong acids are breaking into their ions when put in solutions

  HCl

  H2 SO4

  HNO3
• Weak acid only partially dissociate in a solution like

  citric acid

  carbon acid

  ethanol acid
• Factors that affect the ph is strength and concentration

  if there is a stronger acid it has a weak ph because it is further from 7 whereas a weak acid has a higher ph
• Bases are acids that neutralise acids to form salt and water
• Metal oxides are bases
• Metal oxide(any) + acid= salt + water
• The three different bases acids can react with to form neutral solutions

  acid + metal oxide = salt + water

  acid + metal hydroxide = salt + water

  acid + metal carbonate = salt + water + co2
• A base is anything that can neutralise acid