When selecting an indicator for acid-base titrations, choose an indicator whose pH range falls within the pH change of the reaction. For example, in the titration of a strong acid with a strong base, the pH quickly changes from 3 to 11.
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What are general criteria of choosing a suitable indicator for a given titration?
The indicator should have a broad pH range. The indicator should have neutral point at pH=7. The indicator must show a sharp colour changes near the equivalence point of titration point.
What is a suitable indicator?
The suitable indicators for the following titrations are, (i) Strong acid Vs strong base: Phenolphthalein (pH range 8.3 to 10.5), methyl red (pH range 4.4 – 6.5) and methyl orange (pH range 3.2 to 4.5). (ii) Weak acid Vs strong base: Phenolphthalein. (iii) Strong acid Vs weak base: Methyl red and methyl orange.
What are 3 examples of indicators?
Table of Common pH Indicators
| Indicator | Acid Color | pH Range |
|---|---|---|
| bromothymol blue | yellow | 6.0 – 7.6 |
| phenol red | yellow | 6.8- 8.4 |
| thymol blue (second change) | yellow | 8.0 – 9.6 |
| phenolphthalein | colorless | 8.2 -10.0 |
What makes a good indicator chemistry?
In all cases, though, a good indicator must have the following properties: The color change must be easily detected. The color change must be rapid. The indicator molecule must not react with the substance being titrated.
What are the four criteria that a titration reaction must meet?
Titrations reactions mixture must be (i) rapid; (ii) quantifiable by means of an easily observed end-point; (iii) have known and definite stoichiometry.
What are the theories of indicators?
Ostwald’s Theory
The colour change of any indicator is due to its ionisation. The unionised form of indicator has different colour than its ionised form. An inidicator is either a weak acid or base, so its ionisation is highly affected in acids and bases.
What does Bromothymol blue indicate?
Bromthymol Blue is a dye used as an indicator in determining pH. Bromthymol blue is a weak acid. It can be in acid or base form, depending on the pH of the solution.
Why is phenolphthalein not a suitable indicator?
In the same way in the Titration of weak base versus strong acid there is a sudden change in the pH of 3.5 to 8.0,near the neutralisation point. So Phenolphthalein can’t be used since its pH range is 8.3 to 10.0.
Why is bromocresol green a good indicator?
In aqueous solution, Bromocresol green will ionize to give the monoanionic form (yellow), that further deprotonates at higher pH to give the dianionic form (blue), which is stabilized by resonance.It is used as a pH indicator and as a tracking dye for DNA agarose gel electrophoresis.
What are the 4 types of indicators?
The infographic differentiates between four different types, including trend, momentum, volatility, and volume indicators.
- Trend indicators. These technical indicators measure the direction and strength of a trend by comparing prices to an established baseline.
- Momentum indicators.
- Volatility Indicators.
- Volume Indicators.
What are 5 types of indicators?
Type of indicators
- Input indicators. These indicators refer to the resources needed for the implementation of an activity or intervention.
- Process and output indicators. Process indicators refer to indicators to measure whether planned activities took place.
- Outcome indicators.
- Impact indicators.
What are the four types of indicators?
According to this typology, there are four types of indicators: input, output, outcome and impact.
What happens if you add too much phenolphthalein?
The intensity of the color is concentration dependent, so if a large amount of phenolphthalein is present the color could be very strong at the end-point. However, the presence of a large amount of phenolphthalein is not usually the reason a titration mixture has an intense color.
What color is BCG?
Bromocresol green
Bromocresol green (BCG) is a dye of the triphenylmethane family (triarylmethane dyes).
Bromocresol green.
| Names | |
|---|---|
| 3D model (JSmol) | Interactive image |
| Abbreviations | BCG |
| ChEMBL | ChEMBL145704 |
| ChemSpider | 6209 |
Is turmeric an acid base indicator?
Turmeric is used as a natural indicator. It is added to the solution to determine its acidity and basicity. The turmeric is acidic in nature and it is yellow in color.When turmeric paste is added to the basic solution the yellow color changes to red color due to the neutralization reaction.
How do you accurately read a titration?
Terms in this set (9)
- Meniscus at eye level. To avoid parallax error.
- White tile. To see end point clearer.
- Remove funnel before titrating. Increases the vol making the titre smaller.
- Dropwise addition.
- No bubbles in pipette & burette at the tip.
- Swirling during titration.
- Few drops of indicator.
- Repeat the titration.
How do indicators work?
Indicators are substances whose solutions change color due to changes in pH. These are called acid-base indicators. They are usually weak acids or bases, but their conjugate base or acid forms have different colors due to differences in their absorption spectra.
Do indicators have pH?
Hence, a pH indicator is a chemical detector for hydronium ions (H3O+) or hydrogen ions (H+) in the Arrhenius model.
Universal Indicator.
| pH range | Description | Colour |
|---|---|---|
| 3 – 6 | Weak acid | Orange/Yellow |
| 7 | Neutral | Green |
| 8 – 11 | Weak base | Blue |
| 11-14 | Strong base | Violet/Indigo |
How many indicator Theorys are there?
Theory of acid-base indicators: Two theories have been proposed to explain the change of colour of acid-base indicators with change in pH. 1. Ostwald’s theory: According to this theory: (a) The colour change is due to ionisation of the acid-base indicator.
What is an indicator chemistry?
chemical indicator, any substance that gives a visible sign, usually by a colour change, of the presence or absence of a threshold concentration of a chemical species, such as an acid or an alkali in a solution. An example is the substance called methyl yellow, which imparts a yellow colour to an alkaline solution.