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

To study the action of a buffer solution

Extracts from this document...

Introduction

EXPERIMENT ( 14 ) Topic : To study the action of a buffer solution Introduction : In this experiment, you are to compare the effects of adding small amounts of acid and alkali to buffered and unbuffered solutions of the same pH. You are provided with a buffer solution designed to maintain a pH of 7.0 at 25OC and some pure water which, if it is pure enough, should also have a pH of 7.0 at 25OC. To samples of these 2 liquids, you add small measured amounts of 0.1M NaOH and 0.1M HCl, measuring the pH at each addition. By comparing the pH changes in the 2 solutions, you can demonstrate the action of a buffer solution. Chemicals : 0.1M HCl(aq) , 0.1M NaOH(aq) , Distilled water , Buffer solution (pH 7.0) , Pure water (freshly-boiled distilled water) Procedures : Part A : Effect of NaOH on pH of buffer solution (pre-set at pH 7) 1. Fill a burette with 0.1M NaOH. 2. Using a measuring cylinder, put 25 cm3 of the buffer solution in a 50 cm3 beaker. 3. Rinse the pH meter electrode with distilled water from a wash-bottle, and put it into the beaker, making sure that the glass bulb is completely immersed. ...read more.

Middle

After adding NaOH into buufer solution, ethanoic acid will react with OH- to form salt and water. The equation is: CH3COOH + OH- CH3COO- + H2O The pH of the buffer solution only slightly rises from 7.0 to 7.4. The pH value can be calculated by this equation: pH = pKa + log [A-]/[HA] Since Ka is the equilibrium constant of the reaction, the pH value is only affected by the ratio of concentration of CH3COO- and CH3COOH. Because the ratio is in log form, the pH value will have a smaller change. 2. Explain, by using suitable equations, the effect of HCl on pH of buffer solution. After adding HCl into buufer solution, ethanoate will react with H+ to form ethanoic acid and water. The equation is: CH3COO- + H+CH3COOH + H2O The pH of the buffer solution only slightly drops from 7.2 to 6.4. The pH value can be calculated by this equation: pH = pKa + log [A-]/[HA] Since Ka is the equilibrium constant of the reaction, the pH value is only affected by the ratio of concentration of CH3COO- and CH3COOH. Because the ratio is in log form, the pH value will have a smaller change. ...read more.

Conclusion

Then, CH3COO- and H2O will be formed as a product. NaOH + CH3COOH CH3COO-Na+ + H2O Secondly, mix the sodium ethanoate solution and ethanoic acid together into a beaker. Put the data into this equation: pH = pKa + log [CH3COO-]/[ CH3COOH] 5.2 = -log (1.8x10-5) + log [CH3COO-]/1.0 5.2-4.74 = log [CH3COO-] 0.46 = log [CH3COO-] [CH3COO-] = 2.85M If 1 dm3 of the buffer solution is produced, the number of mole that CH3COO- needed =2.85(1) = 2.85 mole. Number of mole of CH3COO- = Number of mole of NaOH So the mass of NaOH that needed to use for making pH 5.2 buffer is 2.85 X (23+16+1) = 114g 10. Explain how could you measure Ka of 1.0M CH3COOH by using the following : (Given : 1.0M CH3COOH(aq) , 1.0M NaOH(aq) , pH meter) Firstly, add 1.0M NaOH(aq) into 1.0M CH3COOH. Then, CH3COO- and H2O will be formed as a product. NaOH + CH3COOH CH3COO-Na+ + H2O Secondly, mix the sodium ethanoate solution and ethanoic acid together into a beaker. The mixed solution is the buffer solution that we want to find its pH. Finally, put the electrode that belongs to pH meter into the buffer solution. The reading on the pH meter shows the pH of this buffer solution. ...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 Inorganic 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 Inorganic Chemistry essays

  1. Peer reviewed

    Determining the concentration of acid in a given solution

    5 star(s)

    Measuring the sodium carbonate solution 1 2 I need to make 250cm3 of a sodium hydroxide solution with the concentration of 0.1 mol dm-3. I will use solid hydrated sodium carbonate with the formula Na2CO3�10H2O.1 Mr (Na2CO3�10H2O) = (23+23+12+48+20+160) = 286 250cm3 of 0.1 mol dm-3 contains (0.1 x 250/1000)

  2. effects Concentration and Temperature on the Rate of Reaction

    I believe this will help me in obtaining accurate results. Temperature of Reactants (°C) Time Take For the Mixture to Turn Colourless (seconds) 10 101.5 20 23.7 30 10.2 40 5.1 50 1.9 60 0.8 I also conducted a pre-test to trial my method for investigating how temperature change affects the reaction rate.

  1. Determining an Equilibrium Constant

    3.> Add 2 - 3 drops of phenolphthalein indicator and titrate the mixture with standardized NaOH solution. 4.> Repeat steps 2 - 3 for other regent bottles. The results are recorded in Table 2. Table 2 shows the results of titration: Concentration of NaOH(aq)

  2. Bleaching experiment. Estimation of available chlorine in commercial bleaching solution.

    Page 5 (5)Why the available chlorine of old bleaching solution is lower than that of a new one? Available chlorine of old bleaching solution is lower than that of a new one because: First, bleaching solution may deteriorate due to the attack or decomposition by carbon dioxide in air according to the equation: 2ClO-(aq)

  1. Aim To study the effect of concentration of iodide ion ...

    For some time, no changes were detected. Suddenly, the mixture in the flask turned into a blue-black solution. The blue-black intensified as time passed by. Concentration of KI, Time for blue-black solution to form, t / s ( � 0.01s)

  2. Chemistry - Data Analysis

    This is due to convection, conduction and radiation. Paper Cup cooled the fastest Plastic cup The results show that initially the water-cooled down rapidly then between the 18th and 26th minute it cooled down slower. The plastic cup was placed inside a beaker, which could have affected the rate in which the water-cooled.

  1. The Chemistry oh Phosphorous

    Red phosphorus is also used by the military, however because it is less reactive and does not ignite spontaneously, its usage is limited to smoke-screening and less for incendiary weapons. However this is not its main use. Originally matches were made by coating the match head in a mixture containing

  2. Standardizing a Sodium Hydroxide (NaOH) Solution

    = 1.568 moldm -6 d) Molarity calculation of sodium hydroxide solution Molar ration of HKC8O4H4 to NaOH is 1.1. Therefore the mole of HKC8O4H4 are the same as NaOH which is 0.0245mol. Molartiy of NaOH = 0.0245mol/ (26.00cm3 / 1000)

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