paper 1 chemistry

• exothermic reactions release heat energy into the surroundings
• endothermic reactions absorb heat from the surroundings
• atom economy = $\frac{mr\ of\ desired\ product}{mr\ of\ all\ reactats}$ x 100
• percentage yield = $\frac{mass\ of\ product\ actually\ made}{\max imum\ theoretical\ mass\ of\ product}$ x 100
• filtration separates insoluable solids from liquids
• evaporation & crystallisation separate soluable solids from solutions
• when non-metal atoms bond together, they share pairs of electrons to form covalent bonds
• when a non-metal atom bonds with a metal atom they transfer electrons to create ionic bonds and positively/negatively charged ions
• oxidation is loss of electrons (metals)
• reduction is gain of electrons (non-metals)
• positive ions = cations
• negative ions = anions
• titrations is where a solution of known concentrations is gradually added through a burette to another solution to find the concentration of this solution
• titration between acid and alkali: colourless = acid, pink = alkali
• electrolyte must be molten for the ions to move
• electrolysis: chemical decomposition produced by passing an electric current through a liquid or solution containing ions.
• in electrolysis, the positive ions more towards the cathode and gain electrons (reduction)
• in electrolysis, the negative ions move towards the anode and lose electrons (oxidation)
• at the cathode, $H^+$ ions are present
• at the anode $OH^-$ ions are present
• volume of gas ( $dm^3$ ) = $\frac{mass\ of\ gas\ \left(g\right)}{mr\ of\ gas}$ x 24
• concentration (g/ $dm^3$ ) = $\frac{mass\ of\ solute\ \left(g\right)}{volume\ of\ solvent\ \left(dm3\right)}$
• percentage mass of an element in a compound = $\frac{Ar\ x\ number\ of\ atoms\ of\ that\ element}{Mr\ of\ the\ compound}$ x 100
• reactivity series:

  • potassium (K)
  • sodium (Na)
  • lithium (Li)
  • calcium (Ca)
  • magnesium (Mg)
  • carbon (C)
  • zinc (Zn)
  • iron (Fe)
  • hydrogen (H)
  • copper (Cu)
• the higher a metal is in the reactivity series, the more easily it reacts with water or acid.
• acid + metal -> salt + hydrogen
• metal + water -> metal hydroxide + hydrogen
• formation of metal ore = oxidation
• extraction of metal = reduction
• if electrons are transferred, it is a redox reaction
• metals reacting with acids is an example of a redox reaction
• a more reactive metal will displace a less reactive metal from its compound
• metal displacement reactions are redox reactions
• example of a redox reaction (metal displacement):

  iron + copper sulfate -> iron sulfate + copper

  iron is more reactive than copper, so iron displaces the copper from the compound
• graphite is made up of layers of graphene, which slide over each other, giving graphite a slippery feel and allowing it to conduct electricity
• graphite and diamond are giant covalent structures made up of carbon atoms
• unlike graphite, diamond cannot conduct electricity because it has no delocalised electrons
• alloys are harder than pure metals because they are made up of two different metals, which have different sized atoms. the different sized metal atoms make it more difficult for the layers to slide over each other
• metals are malleable and good conductors of electricity and heat
• metallic bonding is the electrostatic forces of attraction between the positive ions and the shared delocalised electrons