indicators (acid + alkali) Flashcards
1
Q
what colour does litmus start off with?
A
purple
2
Q
what colour does phenolphthalein start off with?
A
colourless
3
Q
what colour does methyl orange start off with?
A
orange
4
Q
what colour does bromothymol blue start off with?
A
orange
5
Q
litmus result with acid
A
purple → red
6
Q
litmus result with alkali
A
purple → blue
7
Q
phenolphthalein result with acid
A
colourless → colourless
[no change]
8
Q
phenolphthalein result with alkali
A
colourless → pink (cerise)
9
Q
methyl orange result with acid
A
orange → red
10
Q
methyl orange result with alkali
A
orange → yellow
11
Q
bromothymol blue result with acid
A
orange → yellow
12
Q
bromothymol blue result with alkali
A
orange → blue
13
Q
why do indicators change colour?
A
there is a reversable chemical change between the indicator molecules and the acids or alkalis.
