• 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

Experiment to demonstrate the effects of buffers on ph changes.

Extracts from this document...

Introduction

1.0 Title: Buffer and pH changes ________________ 2.0 Abstract: In the beginning, processes are affected by the hydrogen ion concentration and the control of pH is important in organisms and their cells because chemical reactions like for an example, the ambient pH affects the enzyme function. However, some side chains of amino acids (R-groups) have ionizable groups like carboxyl or amine groups but changes in pH can alter the number of positively and negatively charged groups. Furthermore, the net charge on the protein effects its three-dimensional structure and thus causing it to have an enzymatic activity. Also, when working with living systems in a laboratory it is necessary to pay close attention to the pH of solutions for that same reasons. Moreover, chemicals that tend to prevent changes in the concentration of hydrogen ions are buffers which are chemicals or combinations. In the lab, we will learn about some buffered solutions to gain a further understanding of how buffers work and to observe the range of buffering capacity. When analysing the data, will make use of graphs and see the relationship of pH to pKa using the Henderson-Hasselbalch equation. In general, buffers are composed of mixtures of weak acids and their corresponding salts and by using the Lowry Bronstead definition, an acid is a compound that can donate a hydrogen ion. However, a weak acid is one that does not completely dissociate or ionize, in a solution. ...read more.

Middle

The Determination of Buffering Action toward Base Beaker Num. Solution Initial pH Value Final pH Value 6 Water 6 13 7 Sodium Chloride 6 14 8 1g of Solid Sodium Acetate 6 13 9 5g of Solid Sodium Acetate 6 13 10 10g of Solid Sodium Acetate 7 7 ________________ Discussion: 1. From your results in this experiment, which solution of those you tested had the greatest buffer capacity: * Toward strong acid? * Toward strong base? Discuss. Buffer capacity is the ability of a solution to resist changes in pH by either absorbing or desorbing H+ and OH- ions when small amount of acid or base is added. Buffer capacity is also a quantitative measure of resistance to pH change upon the addition of H+ or OH- ions. From the results of the experiment, solution in test tube 5 had the greatest buffer capacity toward strong acid, which is 10g of solid sodium acetate (CH3COONa) added with 50 ml 0.1 M acetic acid. This solution has the smallest change in the pH value when 1 ml 6.0 M hydrochloric acid is added into it. The pH value is changed from 8 to 7. With the addition of hydrochloric acid (HCl), the increase of H+ ions are counteracted with the excess of acetate ions to form CH3COOH. Thus, the added H+ ions are neutralized and the pH of the buffer solution is changed. ...read more.

Conclusion

concentration to increase by less than the quantity expected for the amount of strong acid added. Correspondingly, when a strong base is added to the mixture, the hydrogen ion concentration (H+) decreases by less than the quantity expected for the amount of base added. This is because the reaction shifts to the right to accommodate for the loss of hydrogen ion (H+) in the reaction with the base. ________________ 6.0 Conclusion: In a nutshell, we are able to understand the nature of buffer. In other words, we could define nature of buffer in which solution that resists a change in pH when acids or bases are added. Besides, we are able to prepare a buffer from acetic acid and sodium acetate. Sodium acetate is a weakly basic salt and the conjugate of acetic acid. A mixture of sodium acetate and acetic acid makes good buffer for a weakly acidic solution. If hydrochloric acid is added to acetate or acetic solution, the hydronium ions produced by the nearly complete dissociation of the hydrochloric acid react with the acetate ions to form molecular (non-dissociated) acetic acid. According to Le Chatelier?s Principle, the equilibrium is forced to the left, reducing the concentration of hydronium and acetate ions, and increasing the concentration of the molecular acetic acid in the solution. If sodium hydroxide is added to the buffer solution, the NaOH ionizes completely in solution, yielding hydroxide ions and sodium ions. According to Le Chatelier?s Principle, the increase in hydroxide ions forces the acetic acid equilibrium to the right, decreasing the concentration of hydroxide ions and increasing the concentration of acetate ions. ________________ 7. ...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

    Write an account of buffer solutions.

    5 star(s)

    Since ethanoic acid is a weak acid, the equilibrium is well to the right: CH3COO- + H3O+ CH3COOH + H2O (eqn. 2) In this way, most of the hydroxonium ions are removed by ethanoate ions, and thus the pH of solution is not altered to a great degree.

  2. Free essay

    Determining an Equilibrium constant

    Amount of HCl /mol 0.0097 0.0097 0.0097 0.0097 0.0097 0.0097 2. Total amount of acid at eqm. /mol 0.0259 0.0267 0.0231 0.0225 0.0210 0.0233 3. Eqm. amount of ethanoic acid /mol 0.0162 0.0170 0.0134 0.0128 0.0113 0.0136 4. Eqm. amount of ethanol /mol 0.0162 0.0170 0.0134 0.0128 0.0113 0.0136 5.

  1. Investigating how concentration affects rate of reaction

    Cough. Dizziness. Headache. Nausea. Vomiting. Shortness of breath. Laboured breathing. Unconsciousness. Avoid inhalation of fine dust and mist. Ventilation or breathing protection. Fresh air, rest. Half-upright position. Refer for medical attention. Contact with skin Easily absorbed. Serious skin burns. Numbness. Convulsion. Collapse. Coma. Death. Protective gloves. Protective clothing.

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

    If any glass is broken, it will be brought to the attention of those in the lab immediately. Then, I will clear it up with a dust pan and brush and put it into a glass bin. Then I will check for small pieces of glass which I may have missed.

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

    Ethyl ethanoate and hydrochloric acid were colourless. 3. Ethyl ethanoate had a "glue" smell. Part B: 4. The colour of the end-point of the titrations was from colourless to pink. 5. The liquid mixtures were miscible and remained colourless after a week.

  2. Objective:-To prepare a buffer solution and observe the properties of a buffer

    50 cm3 of 0.1M ethanoic acid was measured using a measuring cylinder and poured into the same beaker. 4. The reaction mixture was stirred with a clean glass rod and marked as solution A. 5. The pH of solution A was measured with the calibrated pH meter.

  1. Experiments to examine dynamic equilibrium and Le Chateliers principle

    solution is added to 100 mL of water in a 250 mL beaker. This stock solution is stirred until it is homogeneous. Observations are recorded. 5 mL of the stock solution is added to a 4" test tube (Tube 1).

  2. Titration - Preparation,Neutralisation and Applications in Industry

    This is usually done to determine how reactive gases are and how they react with other gases which act as the titrant. Gas phase Titrations would be useful in the environmental and science industry it is vital for ozone analysis.

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