• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. 9
  10. 10
  11. 11
  12. 12
  13. 13
  14. 14
  15. 15
  16. 16
  17. 17
  18. 18
  19. 19

How the effect of concentration affects the rate of a chemical reaction

Extracts from this document...


How the effect of concentration affects the rate of a chemical reaction The aim of this investigation is to study how the effect of concentration affects the rate of a chemical reaction. This will be investigated by dissolving magnesium in varying concentrations of hydrochloric acid. The reaction that will take place is as follows: 2HCl (aq) + Mg(s) MgCl2 (aq) + H2 (g) Prediction I predict that as the concentration of acid is increased, the rate of reaction will increase. I also predict that if the concentration were to be doubled, the rate of reaction would also double. Explanation of Prediction I predict that as the concentration of acid is increased, the rate of reaction will increase. This is because the hydrochloric acid is more concentrated and therefore there will be a greater collision frequency between the Magnesium atoms in the solid structure and the H+ ions in solution. A very small percentage of collisions result in a reaction, so if there were to be more collisions (as there will be with a greater concentration of acid), there will be more reactions. The increase in the rate of reaction will be apparent because it will fizz more violently giving off more hydrogen gas, the presence of which can be tested for by igniting the gas. If there is hydrogen gas being given off, a popping sound will be heard. I also predicted that if the concentration were to be doubled, the rate of reaction would also double. This is because the two are directly proportional as if the concentration if doubles, the collision frequency also doubles, so twice as many reactions will take place in a second (as can be seen in the rate/concentration graph below). I predict that graphs of time and rate for the results will look like this: Rate Time (s) Conc of acid (moles) Conc of acid (moles) Time/concentration graph - The line will never touch the x-axis because the reaction will never be instantaneous, and will never touch the y axis because there will be no reaction if there is no acid. ...read more.


Number of moles of magnesium = (100 / 1000) x (1 / 2) * Mass / Ar = Number of moles Mass of Magnesium = 24 (the Ar ) x ( (100 / 1000) x (1 / 2) ) = 1.2g (20cm of Magnesium has a mass of 0.18g - with a defined width) 20cm = 0.18g ( x 6.66) 133.33cm = 1.2g The above calculation has shown that 133cm of magnesium will dissolve in 1Mole Hydrochloric acid. This means that the 1cm lengths used in the experiment will easily dissolve in the acid. Obtaining Evidence The following method was used when performing the experiment: 1. Measure out a defined volume of 2M Hydrochloric acid into a measuring cylinder using a dropping pipette. The level should be read from the bottom of the meniscus and should be read at eye-level with the measuring cylinder on a level surface. This ensures that the exact amount of acid is used every time so the results will be more accurate. 2. If the concentration of acid being used is not 2M acid, a defined volume of water will need to be added to the acid. To find the volume of water needed use the following calculation: 3. Volume of water = 100cm3 - Volume of acid. 4. Pour the liquid into a beaker and measure the temperature of the solution using a thermometer. Record the temperature, the temperature should be the same for every test because if the temperature is increased, the ions have more kinetic energy so will move around faster resulting in harder collisions and more frequent collisions with the Magnesium atoms. This would affect the results. 5. Measure 1cm length of magnesium, and re-measure it before cutting. It is important that the length is exact as the length of Magnesium is a constant in the experiment. 6. Wipe the magnesium with iron wool to remove the oxide layer that will have formed when the magnesium was exposed to the air prior to the experiment. ...read more.


Testing each concentration of Hydrochloric acid two or three times and then calculating the mean average could improve the results. Testing the concentrations in 0.1M increments would give a greater fluidity to the graph line, and would enable the prediction of results for concentrations not yet tested by being able to calculate a more accurate formula for the line. Conclusion My results prove beyond doubt that as the concentration of the acid increases, the time taken for the reaction decreases. For example, my results show that the time taken is 99, 45, 24, 16, 12 and 10s when the concentration of Hydrochloric acid is increased. The results are good enough to support a firm conclusion because they all follow the trend of the time for the reaction decreasing as the concentration of acid increases, and they are all very close to the line of best fit. However, if more concentrations were to be tested, a greater range of results could be recorded, so the results would support the conclusion even more strongly. The results are very reliable because they can all be explained using science. Even if a person with no knowledge of science at all were to view the results, he would say that they are accurate because of their being in very close proximity to the line of best fit. This shows that the results are consistent, which adds to their reliability. Further Work There are numerous ways of obtaining more evidence for the conclusion or extending the investigation. Some of these ways are as follows: 1. Carry out the experiment using a different acid, for example H2SO4 (sulphuric acid) or H2NO3 (nitric acid). Will the results be the same as for Hydrochloric acid? 2. Carry out the experiment for a different group 2 alkali earth metal, for example Calcium (Ca) or Barium (Ba). Will the results be the same as for Magnesium? 3. Carry out the experiment at a different temperature. Will the times for the various reactions be faster or slower than at 20?C? Danny Longman 10JL March 2002 2 ...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 Aqueous Chemistry 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 Aqueous Chemistry essays

  1. Marked by a teacher

    To investigate the effect of temperature on the rate of reaction

    4 star(s)

    To work out the rate of reaction, I chose a point (55 ml) on the y-axis, and joined it to the curve, then to the x-axis. I drew tangents and then read the point off the curve. Rate of reaction = y/x Temperature (oC)

  2. Heat of Reaction - Dissolving Magnesium in acid

    charge 1-, so in order for magnesium to lose two electrons to achieve a full outer shell, and therefore stability, it needs two hydrogen atoms because they can only take one more electron each.) * When the electron transfer has taken place a magnesium ion and two hydrogen atoms have been formed.

  1. Investigation to show how the concentration of an acid effects the rate of its ...

    be more of one and less of another each time, so that this does not effect the chance of collision. By keeping all of these elements the same, I will hopefully gain a set of results, which have not been altered by a change in anything other than concentration.

  2. The rate of reaction between magnesium and sulphuric acid.

    Amount of H? 30 38.5 11.5 cm3 60 25.5 24.5 cm3 90 22.5 27.5 cm3 120 22.5 27.5 cm3 150 22.5 27.5 cm3 180 22.5 27.5 cm3 17ml of Acid: 3ml Water Time measured in seconds Reading on burette (ml)

  1. Investigating the reaction between magnesium and hydrochloric acid.

    Method Firstly I measured out 30ml of 2M hydrochloric acid in a measuring cylinder and poured it into a boiling tube, then I placed the boiling tube in the test tube rack and got a piece of 1cm magnesium strip on standby.

  2. To investigate the rate of reaction between different concentrations of hydrochloric acid with metal ...

    Light intensity Lab conditions-11.50am Problems 1. There is lag of time between the experiment happening, and timing it, as I have to put the Calcium carbonate into the acid, then time it, then put the stopper in. 2. Some of the CO2 will have escaped by that time, therefore, not an accurate experiment.

  1. Determining the purity of Iron Wool.

    An error is more likely to occur during the procedure of the experiment. A viable reason could have been during the heating of the iron wool and Sulphuric acid. The procedure called for full dissolution of the two by heating on a hot plate, if this didn't occur and remnants

  2. To investigate the differences in order of reaction and activation energy of the reactions ...

    If the mechanism of the reaction invoving ethanoic acid is different to that of hydrochloric acid they might be expected to have different rate equations and overall orders if the ionisation of the CH3COOH molecules is the rate determining step.

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