Indicators Flashcards
What are the three common indicators?
1) methyl orange
2) bromothymol blue
3) phenolphthalein
What kind of substance is an indicator?
usually a weak acid or base
What does an indicator do?
display different colours in their complete and un-ionised form than their ionised form
What 3 colours can methyl orange turn?
red, orange, yellow
What 3 colours can bromothymol blue turn?
yellow, green blue
What 3 colours can phenolphthalein turn?
clear, light pink, dark pink
What is a colour change range?
the range in which the indicator changes colour to show pH is going higher or lower than a certain level
What is the colour change range of methyl orange?
3.1 to 4.4
What is the colour change range of bromothymol blue?
6.0 to 7.6
What is the colour change range of phenolphthalein?
8.3 to 10.00
Why is litmus paper not commonly used as an indicator?
it has a wide colour change range, from 4.5 to 8.3, making it hard to pinpoint a general pH
What are the two main types of indicators?
synthetic and natural
What is a synthetic indicator with an example?
a man-made indicator, like bromothymol blue
What is a natural indicator with an example?
an indicator sourced from nature, like litmus is extracted from lichen
What ype of indicator is preferred?
synthetic, because it gives cleared colour changes, and is usually cheaper and easier to get
