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

To determine the indicator range of some acid-base indicators

Extracts from this document...


1. fill burette with deionized water, NaOH, HCl + white tile 2. 1st beaker: 25 HCl + 10 water into beaker 3. 2nd beaker: 25 NaOH +10 water 4. 3rd beaker: 25 buffer + 2 drop of indicator Add more indicator if too pale No of drop 5. Add same no of drop of indicator to 1st and 2nd 6. Dilute HCl with water, vol same as 3rd Dilute NaOH with water, vol same as 3rd 7. Add NaOH 1cm3 at a time to 3rd, mix 8. Measure pH with pH meter just when color change (compare to 1st) 9. Add NaOH 1cm3 at a time to 3rd, mix 10. Measure pH until color change is complete (compare with 2nd ) 11. Repeat with other indicator Indicator pH ( color change start) pH (color change complete) Color 1 Color 2 S.K.H. Lam Woo Memorial Secondary School F.7 Chemistry Laboratory Report Name: Chan Ching Wai Class: F.7H (2) Experiment 4: Indicator Date of Experiment: 16-11-2010 Objective To determine the indicator range of some acid-base indicators Introduction In this experiment, the indicator ranges of some acid-base indicators were determined. Indicators are chemicals that would change color as the pH of the solution in which they are dissolved changes within the indicator range. Indicators are commonly used in acid-base equilibrium in order to determine the concentration of a solution. ...read more.


In this process, the solution in beaker 1 and beaker 2 could be diluted from time to time in order to give fair comparison with color of beaker 3 with the same volume. Results Indicator pH ( color change start) pH (color change complete) Color 1 Color 2 Litmus 6.8 9.9 Pink Blue Phenolphthalein 7.1 10.4 Colorless Pale pink Methyl red 3.3 5.3 Red Pale yellow Methyl orange 4.3 5.6 Red Pale yellow Bromophenol blue 2.6 3.8 Pale yellow Pale purple Discussion Measured in buffer solution The indicator range of indicator was determined by adding sodium hydroxide solution to buffer solution in beaker 3. Beaker 3 should be filled with buffer solution but not deionized water for easy measurement of pH at particular point. To begin with, a buffer solution is a solution which tends to resist pH change when it is diluted or a small amount of acid or bases is added to it. With the ions inside the buffer solution, the acid and base added would be converted into weak acid or weak bases which would only slightly ionized into water. This was because the buffer solution is made of weak acid or weak base with its salt. The salt in buffer solution completely ionized in water to give the salt of the acid or base and the other oppositely charged ion. ...read more.


Thus, the determination of color change is important. Yet, determination by human eyes is not accurate and quite objective. To improve this situation, the color of beaker 3 could be compared with beaker 1 and 2 as stated above. Also, white tile could be placed under the beakers to make the color change more conspicuous. Thirdly, equal number of drops of indicators was added to the three beakers to have fair comparison of the colors. If more drops of indicator are added, the color of the solution would be deeper and did not resemble the initial color of beaker 3. This may lead to an inaccurate determination of the point of color change and a measurement of pH at wrong time. Fourthly, as the sodium hydroxide solution was added 1 cm3 each time, the accuracy could only be corrected to 1 cm3. If color change occurred when an additional amount of 0.5 cm3 added to the solution, an extra amount of 0.5cm3of sodium hydroxide solution may already have been added. Thus, a higher pH would be measured. Therefore, sodium hydroxide solution could be added drop by drop when the color was about to change or stop to change. The pH meter should also be dipped immediately when color started to change or stopped to change so as to measure the pH exactly at these points. Conclusion In this experiment, the indicator range of the following indicators were measured. Indicator Indicator range Litmus 6.8-9.9 Phenolphthalein 7.1-10.4 Methyl red 3.3-5.3 Methyl orange 4.3-5.6 Bromophenol blue 2.6-3.8 ...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 Classics 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 Classics essays

  1. Determination of the Partition Coefficient of Ethanoic Acid between Water and Butan-1-ol

    Question 1. Shaking can increase the surface area for ethanoic acid to contact with both water and butan-1-ol. Also, by shaking, equilibrium state can be attained faster. 2. As butan-1-ol evaporates, pressure is built up in the separating funnel. The tap should be opened occasionally to release pressure built up inside to avoid the breakage of the funnel.

  2. Determining Freezing Point Depression Constant for Acetic Acid

    Procedure 1. MicroLAB is set up to measure the temperature change with temperature in Celsius on the Y axis and time in seconds on the X axis. 2. A clean beaker and test tube were weighed and mass recorded 3. a few mL acetic acid were added to test tube, weighed with beaker and mass was recorded.

  1. Investigation of the effect of changes in ionic concentration on the e.m.f of a ...

    If the two solutions were directly mixed, spontaneous reactions occurred in one cell and most energy was released as the less useful heat. With changes in concentration of the chemical species, the equilibrium position for the above half reactions would change.

  2. Determination of Chlorine and Iodine in Water

    .143mol/.100=1.43 molarity of chlorine #3 .001/.0035=.289mol thiosulfate .289mol/2=.143mol chlorine .143mol/.100=1.43 molarity of chlorine Titration of tap water and Iodine solution 1st titration 2nd titration 3rd titration Tap water Iodine Tap water Iodine Tap water Iodine Initial Volume 14.5mL 4mL 18.5mL 16mL 22mL 4mL final Volume 16.5mL 15mL 18.5mL 16mL 22mL

  1. The Effect of Reactant Concentration on the Rate of a Chemical Reaction

    Thus it can be concluded that our results support the hypothesis; that more concentrated solutions react faster than diluted solutions do. The affect on the reaction rate when varying the amount of water and Na2S2O is that; more concentrated

  2. Analysis of Chlorine in Commercial Bleaching Solutions

    - CIO- ions may be decomposed into Cl- ions and oxygen gas. - Iodine is volatile; it may be lost to the surroundings. - Starch solution is not fresh because it is oxidized.

  1. What was the function of hadrians wall

    The view that Hadrian's Wall was a customs barrier used to tax and control all that came in to and left the Roman Empire, has also been put forward by historians and archaeologists. This is based primarily on the fact that there are such a large amount of gates in the wall.

  2. Why did the Romans invade Britain and how did they affect it?

    The third was pro-Roman and sought help from Rome, allegedly to protect his inheritance. Later, the two anti-Roman brothers demanded the return of the third brother and the two brothers started to take over the land of another pro-Roman leader, Verica, in Britain.

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