C6: rate & extent of chem change

• | mean rate of reaction

  interpret graphs

  • STEEP slope, FAST reaction
  • makes LOTS of product in SHORT AMOUNT OF TIME
  • if slope becomes less steep it shows reaction is SLOWING down; rate of reaction is DECREASING_ this bc lot of reactant molecules ALREADY REACTED and turned into products = fewer reactant molecules available to react
  • line flat means all reactant molecules have already reacted
• | mean rate of reaction

  • gas: measures by cm3
• | mean rate of reaction

  • mean rate = quantity of product formed/reactant used ÷ time taken
• | effect of concentration on rate

  • COLLISION THEORY: chemical reactions only take place when particles COLLIDE with SUFFICIENT ENERGY
  • FREQUENCY: NUMBER OF SUCCESSFUL COLLISIONS PER SECOND
• | effect of concentration on rate

  • HIGHER CONCENTRATION, FASTER REACTION & MORE PRODUCT = steeper line
• | rates of reaction [practical 5]

  effect of concentration

  • so thiosulfate + hydrochloric acid -> sulfur (solid)
  • SULFUR makes solution go CLOUDY = TURBIDITY

  1. use measuring cylinder to put 10cm3 of SODIUM THIOSULFATE into CONICAL FLASK on top of CROSS
  2. add 10cm3 of HYDROCHLORIC ACID into CONICAL FLASK
  3. SWIRL before using STOPWATCH to time how long it takes for it to disappear
  4. repeat & calculate MEAN VALUES for different concentrations of SODIUM THIOSULFATE
• | rates of reaction [practical 5]

  • problems that may occur: different eyesights_ if same cross used then this won’t be one
• | rates of reaction [required practice 5]

  • magnesium + hydrochloric acid -> magnesium chloride + hydrogen
  • use measuring cylinder to put 50cm3 of HYDROCHLORIC ACID into flask
  • attach flask to BUNG & DELIVERY TUBE
  • place tube into container with water
  • place UPTURNED MEASURING CYLINDER with water over the delivery tube
  • add 3cm strip of MAGNESIUM to acid & time it
  • ^ reaction produces HYDROGEN GAS trapped in the measuring cylinder & every 10 second, measure volume of hydrogen gas in measuring cylinder until none given off
• | rates of reaction [required practical 5]

  • these experiments show that the GREATER THE CONCENTRATION of a chemical reaction, the faster the reaction takes place
  • ^ reproducible bc results shown by 2 different experiments
• | effect of surface area

  • MORE COLLISIONS PER SECOND, the rate INCREASES when we INCREASE the SURFACE AREA of a solid reactant