C4

• pH scale

  Measure of how acidic or alkaline a solution is, ranging from 0 to 14 with low numbers being most acidic and high numbers being most alkaline
• Measuring pH

  1. Using indicator (changes color depending on pH)

  2. Using pH probe and meter (electronic, more accurate)
• Acid

  Substance that forms aqueous solutions with pH less than 7, releases hydrogen ions in water
• Base

  Substance with pH greater than 7
• Alkali

  Soluble base that forms a solution with pH greater than 7, forms hydroxide ions in water
• Neutralization reaction

  Acid + base → salt + water
• Neutralization reactions produce a pH of 7 (neutral)
• what is electrolysis?

  passing of an electric current through electrolyte. the ions move towards the electrodes and compound decomposes.
• what is an anode?

  positive electrode where oxidation occurs

  made of carbon - needs to be replaced regularly as it reacts with oxygen to produce carbon dioxide.
• what is a cathode?

  negative electrode where reduction occurs.
• what is electrolyte?

  liquid/solution which conducts electricity.
• what is PH?

  measure of the concentration of hydrogen ions.
• how does the PH scale work?

  when the PH scale decreases by 1 , the concentration of hydrogen increases by 10.
• what is the difference between the strength of an acid and it's concentration?

  strong acids - what proportion of the acid molecules ionise in water.

  concentration - how much acid there is in a certain volume of water.
• where in the reactivity series do metals react most easit with water/acid?

  higher in the reactivity series , more easily reacts with water or acid.
• what meals react explosively?

  potassium, sodium, litium and calcium react explosively and lots of bubbles produced.
• what metals react less violently?

  magnesium , zinc and iron react less violently . copper does not react at all
• what happens when metal reacts with water?

  metal + water = metal hydroxide + hydrogen
• what is an example of oxidation?

  common metals react with oxygen to form oxides.
• what is a reduction reaction?

  reduction reaction - separates a metal from it's oxide.
• what metals can/can't be reduced using carbon and why?

  metals higher than carbon ; have to use electrolysis because carbon can only take oxygen away from metals which are less reactive.
• what metals can be extracted by reduction?

  metals below carbon ; can be extracted by reduction using carbon.
• acid + metal ->

  salt + hydrogen
• acid + metal oxide ->

  salt + water
• acid + metal hydroxide ->

  salt + water
• acid + metal base ->

  salt + water
• acid + metal carbonate ->

  salt + water + carbonate
• acids produce H+ ions (hydrogen)