• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Detail, with appropriate scientific theory, the five main factors that affect the rate of a reaction

Extracts from this document...

Introduction

Detail, with appropriate scientific theory, the five main factors that affect the rate of a reaction A chemical reaction involves the breaking of bonds within the reactants and the creation of bonds to form products. Different bonds have different strengths so the energy required for various reactions to occur is different. The rate at which a reaction progresses is controlled by five main factors: - concentration, pressure, temperature, surface area and catalysis. A reaction profile is a graph that shows the energy changes involved during a reaction against time. The basic structure for an exothermic reaction is: - The graph shows that in the intermediate transition stage the reactants have gained more energy from their original form, and then go on to another energy level as products. The graph shows the activation energy required and the energy released. For an endothermic reaction, the reaction profile is similar except the products finish on a higher energy level, thus showing that energy has gone into the reactants to form the products. The collision theory is a theory used to explain rates of reaction. ...read more.

Middle

Also they will be moving more rapidly so the frequency of collisions will be greater resulting in more reactions and thus a higher rate of reaction. The molecules in a gas or liquid do not all have the same kinetic energies since they are moving with different speeds. The distribution of their speeds is called the Maxwell-Boltzmann distribution. The graphs that can be drawn to display this show, why at higher temperatures the rate of a reaction increases. The graph shows that at any temperature, only a few molecules will have very high or very low energies, with most having a value around a mean peak value. As the temperature increases the curve broadens out and the peak value drops moving towards a higher energy level. The area under each curve represents the number of molecules and is constant for each curve. The graph shows that to the right of the E act line, the molecules have enough energy for a reaction to occur. At the higher temperature (T3) a high proportion of the molecules have enough energy to react so the rate of the reaction is higher than at low temperatures (T1) ...read more.

Conclusion

They are generally only required in small amounts. They usually work by providing an alternate route from reactants to products, which has lower activation energy. The simplified reaction profile for such reactions is: - The graph shows simply that with the aid of a catalyst the activation energy required for the reaction is lowered so more of the molecules will have the energy required so the reaction will progress at a faster rate. An example of a catalysed reaction is that between peroxodisulphate ions and iodide ions: S2O82- (AQ) + 2I-(AQ) 2SO42-(AQ) + I2 (AQ) This reaction can be catalysed by Fe2+ ions, two reactions occur: S2O82- (AQ) + 2Fe2+(AQ) 2SO42-(AQ) + 2Fe3+(AQ) Followed by: 2Fe3+(AQ) + 2I-(AQ) 2Fe2+(AQ) + I2 (AQ) The catalyst is changed in the intermediate stage but at the end of the reaction is back in its original state. A reaction profile can be drawn for this reaction although it only shows a theory as to how the process works: - The graph shows the reactants and products along with the two-step intermediate stage where two reactions occur. Overall this reaction is exothermic. Andrew Roberts ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Patterns of Behaviour section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Patterns of Behaviour essays

  1. Exothermic and endothermic reactions

    The Answer O (oxygen) Examiner's Note Well done! The periodic table can tell you what type of ions an element can form. For metals in groups I to III the charge on the ion is + and is the same as the group number e.g. Al3+. For non-metal ions in groups V to VII, the charge is the group number minus 8.

  2. 'Investigating factors that affect the rate of chemical reactions.'

    Sometimes even with care, things might go wrong. For this reason it helps to perform the experiment several times and measure the results, then average them. This increases the reliability and decreases the chance of drawing a false conclusion of there is a wrong or outlying result. Apparatus. The experiment involves reacting a liquid (aqueous dilute hydrochloric acid)

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work