• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
Page
  1. 1
    1
  2. 2
    2
  3. 3
    3
  4. 4
    4
  5. 5
    5
  6. 6
    6
  7. 7
    7
  8. 8
    8
  9. 9
    9
  10. 10
    10
  11. 11
    11
  12. 12
    12
  13. 13
    13
  14. 14
    14
  15. 15
    15
  16. 16
    16
  17. 17
    17
  18. 18
    18
  19. 19
    19
  20. 20
    20

The Determination of rate equation

Extracts from this document...

Introduction

The determination of rate equation Aim: The aim of this investigation is to determine the rate equation of the reaction between sodium thiosulphate Na2S2O3 (aq) and hydrochloric acid HCl (aq), using a graphical method. Background information The experiment is based on the effect of varying the concentration of the respective solutions and finding out the effect it has on the rate of the reaction; in this investigation i will change both sodium thiosulphate and hydrochloric acid. When hydrochloric acid is in excess to the sodium thiosulphate, the reaction may be different to when sodium thiosulphate is in excess. This will show the effect of change in concentration on the rate of reaction. Even though the reaction equation is known, it is not possible to work out the rate equation from the reaction equation and therefore the experiment has to be conducted. Theory: The rate of a reaction can be explained in terms of the rate of decrease in concentration of a reactant or the rate of increase in concentration of a product. The most general method used to determine the rate of reaction is to measure the change in concentration of the reactant(s) per second. The rate of a reaction may be represented by a mathematical equation related to the chemical equation for a reaction. Rate equation has the form rate = k [A]x [B]y which shows how the rate of a chemical reaction depends on the concentration of the reactants (A&B) and the rate constant k. A rate equation is used to describe how the concentration of a product increases or the concentration of the reactants decreases with time, the equation also indicates how the concentration of one or more reactants directly affects the rate. Occasionally it can even be the concentration of a product that affects the rate. In general the rate equation for the reaction: A + B C + D Is found by experiment to follow simple kinetics with the rate equation being written as: Rate = k [A]x[B]y k = rate constant, x = order with respect to [A], y = order with respect with [B]. ...read more.

Middle

3. Lay out all the equipment as shown bellow. 4. Label each test tube with the correct concentration level and organise them in ascending order, to prevent contamination. 5. Label the Graduated pipettes and the beakers for different chemicals to prevent contamination as HCl, Na2S2O3 and H2O are all clear liquid solution. 6. Pour HCl and Na2S2O3 into the correct labelled beaker from the main source. 7. Using the graduated pipette measure 4cm3of HCl and pour into the intended test tube in the test tube rack as shown below: 8. Then measure 41 cm3 of water into the HCl in the test tube and shake the solutions to dilute the HCl. 9. Measure 10cm3 of Na2S2O3 using the graduated pipette and pour it into the other labelled test tube. 10. Using a black marker pen draw a thick cross on the white tile as shown below; 11. Then place the white tile with the cross under the test tube of the diluted HCl as shown bellow. 12. Then add the 10cm3 of Na2S2O3 from the test tube and start the stop watch immediate. 13. Allow the same person to observe through out the whole experiment to make the practical more reliable. 14. Stop the stop watch when the cross is not visible through the solution from the birds eye view in other words when the solution becomes milky/cloudy. 15. Record the result in the result table shown below: Volume of HCl / cm3 Volume of H2O / cm3 Time taken for solution to become milky/ s Experiment 1 Experiment 2 Experiment 3 Average 4.00 41.00 8.00 37.00 12.00 33.00 16.00 29.00 20.00 25.00 16. Repeat the experiment with the same amount of HCl, Na2S2O3 and H2O another 2 times and record the result to make the experiment reliable and the data collected valid. 17. Now repeat the whole experiment using different ranges shown bellow: During these stages distilled water will be used to dilute the HCl and the volume of Na2S2O3 will be the same for the fist experiment. ...read more.

Conclusion

Identify those errors that are significant and justify your choice - justify improvements to the measurement A noticeable effect and the most significant measurement error on the rate of reaction which could have lead errors in measurement could have being; using naked eye to approach conclusion on the rate of reaction, the main problem with using a naked eye is that different people have different eyesight, even though the same person observed the rate of reaction through out the whole experiment, I believe this was not very accurate as even one second delay on the stopping the stop watch could cause an anomaly and also the fact that the person observing the reaction will not get the same clearness in each experiment will make difference in the result therefore instead of using naked eye I will next time use a colorimeter to measure the rate of reaction. Colorimeter is equipment used to measure the colour change in a reaction. By using this devise it will improve accuracy of the experiment as it will exactly tell me how long the rate of reaction has taken place for. Another factor which leaves a margin for error to certain extent was the equipment used to measure the reagents. The accuracies of each burette for example may differ slightly, which may affect the outcome of the experiment, as different burettes were used to measure different solutions. I noticed that it was very difficult to maintain the meniscus of the reagent on the mark as the burette was filled because some times air bubble were formed in the burette, This as a result leaves margin for error. When reading the burettes I was at the level of the graduation to avoid parallax error. The burette used to measure different reagents has an error of + 0.005 and hence may have affected the accuracy of the results obtained. To modify this error I would next time use a digital burette as it would measure the exact amount of reagent required in electric digits and therefore would improve the reliability and accuracy of the solution measured further. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Physical 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 AS and A Level Physical Chemistry essays

  1. Marked by a teacher

    Finding out how much acid there is in a solution

    needed because, this is what helps to dilute the anhydrous sodium carbonate into a solution. 400 ml is a rough calculation of how much distilled water may be needed. This is because, at the end of the preparation of the sodium carbonate solution, 400 ml is supposed to be made (this is explained later in the next section).

  2. To find out how the concentration of hydrochloric acid affects the rate of its ...

    We also had a few lessons at different times of the day. This might have meant that there was a class in the lab before we went in. This can cause the room temperature to change slightly, which would alter the amount of energy in which the particles had.

  1. Free essay

    Determining an Equilibrium constant

    6. Error: Due to some measuring error, the amount of HCl is not the same so equilibrium amount of ethanoic acid obtained are not accurate which in turn affect Kc Improvement: use instrument with smaller graduation. Questions and answers 1. By Le Chatelier's principle, when a system at equilibrium is disturbed

  2. Determining an equilibrium constant. The aim of this experiment is to calculate the ...

    added/ g 4.929 4.943 4.936 4.930 4.959 Mass of water added/ g 0 0 0 1.240 3.032 Part B: Molarity of the standard sodium hydroxide = 1.0086 mol dm-3 Tube 1A 1B 2 3 4 Final burette reading 13.30 22.95 38.85 36.20 28.50 Initial burette reading 3.50 13.30 1.80 3.25

  1. Investigating the rate of reaction between peroxydisulphate(VI) ions and iodide ions

    This will create more accurate and consistent results. Place this into the water bath. See Figure 3.2 below. Table 3.6. A table to show the concentrations making up mixture 3 used in this investigation Volume (cm3) of KI(aq) Volume (cm3) of water Volume (cm3) of Na2S2O3(aq) Volume (cm3)

  2. We are aiming to accurately prepare a standard solution of 0.1 M (mol dm-3) ...

    24.4 24.6 24.7 Initial Volume (cm3) 50 50 50 Volume Used (cm3) 25.6 25.4 25.3 Average Volume Used (cm3) V1 25.433333 M1=concentration of hydrochloric acid (HCl) = M2=concentration of sodium carbonate (Na2CO3) = 0.1 M V1=average volume of acid used = 25.4333cm3 V2=volume of Na2CO3 used = 25cm3 N1= number

  1. Lab Report. Objectives 1. To determine the enthalpy of neutralization of strong acid and ...

    Actually, they should have the same âHn value because HCl and HNO3 are strong acids. Strong acid and strong base will ionize completely in water and the actual ΔHn value for strong acid and strong base is -57 kJ/mol. In my opinion, the major weakness of this experiment is the lost of significant amount of heat to the surrounding.

  2. This investigation is an investigation to find the concentration of two unknown solutions, Na0H ...

    This could mean that chemicals present in the burette or conical flask may have caused the Sodium Hydroxide using a smaller amount of Hydrochloric acid. During the titration, measuring accuracy of the equipment have to be taken into account. The pipette has an accuracy of ±0.06cm3 meaning the accuracy of the equipment is pretty good.

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