MIDTERM 2 pH Indicators Flashcards Preview

BIMM 121 > MIDTERM 2 pH Indicators > Flashcards

Flashcards in MIDTERM 2 pH Indicators Deck (14):
1

Purpose of pH indicators

To identify unknown organisms/ to characterize the behavior of organisms based on the production of acidic/alkaline products ( or the removal of acidic or alkaline substrates from a medium )

2

Where are most pH indicators derived from?

originally derived from plants for use as dyes

3

how does a pH indicator work?

1. They change in color with a change in pH
2. change color when they bind hydrogen or hydroxyl ions in solution

4

How to know which pH indicator to use?

Each of the dyes used as a pH indicator has a defined pH range in which it may be used

5

True or false: more pH indicators are used to detect acid production than alkali production

True

6

Common feature of most pH indicators?

the color change from the starting color is not visually indentifiable until some percentage of the dye ( at least 10%) has changed its state of protonation

7

Problem with pH indicators?

In between two distinct color states, the color continues to change with the change in pH but the incremental color changes are not sufficiently distinct to indentify as a specific color.

8

How to interpret phenol red pH indicator

1. Phenol red changes from red-->yellow
2. It goes from several shades of reddish yellow or yellowish red that are difficult to interpret.

9

What is Standard diagnostic procedure?

A reaction is not designated as positive until all the dye has completed the color change and any intermediate color is designated as a negative result

10

What allows pH indicators to be sensitive to small amounts of acid or alkali production and the pH range of these indicators to be around 2 pH unit?

Most dyes are intensely colored, the concentration of the dye used is usually small and the amount of acid or alkali that is required to complete the color change is small as well

11

Methly Red statistics? Low pH color, Transition pH range, and high pH color

1. low pH color = Red
2. Transition pH range = 4.4-6.2
3. High pH color = yellow

12

Bromothymol Blue statistics? Low pH color, Transition pH range, and high pH color

1. low pH color = yellow
2. Transition pH range = 6.0-7.6
3. High pH color = blue

13

Phenol Red statistics? Low pH color, Transition pH range, and high pH color

1. low pH color = yellow
2. Transition pH range = 6.8-8.4
3. High pH color = red

14

Neutral Red statistics? Low pH color, Transition pH range, and high pH color

1. low pH color = red
2. Transition pH range = 6.8-8.0
3. High pH color = yellow