10D- comparing pH measurements Flashcards
Define commercial indicator
An artificially prepared indicator
Define indicator
A substance that changes colour to indicate a pH range
Define litmus paper
Paper used to indicate the acidity or basicity of a substance
Define natural indicator
An indicator made from naturally sourced substances
Define pH meter
An instrument used to measure the pH of a substance
Acidity
definition(adj.)
-Acidity(adj.)=The
amount of acid in a substance
Alkalinity
definition(adj.)
-Alkalinity(adj.)=The
ability to neutralise an acid
Definition of proticity(aka basicity)
The number of replaceable hydrogens in the formula of an inorganic acid is called Basicity. Basicity is also known as Proticity
Define super acid
Super acid
definition=A superacid can be defined as an acid that is stronger than 100%
sulfuric acid.
Define super base
Inchemistry, asuperbaseis an extremely strongbase. There is no commonly accepted
definition for what qualifies as a superbase, but most chemists would
acceptsodium hydroxideas a ‘benchmark’ base just
assulfuric acidis a ‘benchmark’ acid
(seesuperacid).
how can we approximate pH
indicators- chemical compounds that change colours depending on the pH they are immersed in
what colour does litmus paper turn
blue litmus paper turns red in an acidic solution
red litmus paper turns blue in a basic solution
what are natural indicators
an indicator made from naturally sourced substances
what are commercial indicators
indicators that are prepared artificially
Felix=Indicators that are synthesised/man made
list some natural indicators
red litmus
blue litmus
turmeric
red cabbage juice
Coloured petals of some flowers such as hydrangea
list some commercial indicators
phenolphthalein
methyl violet
methyl orange
thymolphthalein
Universal indicator
what does red litmus paper indicate
acid: red
base: blue
changes colour at pH of=7(CHECK)
what does blue litmus paper indicate
acid: blue
base: red
changes colour at pH of=7(CHECK)
what does turmeric indicate
acid: yellow
base: reddish brown
changes colour at pH of=7.4 and 8.6
what does red cabbage juice indicate
acid: reddish
base: greenish yellow
changes colour at pH of=7
what does phenolphthalein indicate
acid: colourless
base: pink
changes colour at pH of=8.3-10.0
what does methyl violet indicate
acid: yellow
base: blue
changes colour at pH of=0.0-1.6
what does methyl orange indicate
acid: red
base: yellow
changes colour at pH of=3.1-4.4
what does thymolphthalein indicate
acid: colourless
base: blue
changes colour at pH of= 9.3 - 10.5
how can more specific pH measurements be obtained
pH meters can be used to provide a specific, quantitative measurement of pH
they measure the difference in electrical potential between two probes due to the concentration of charged particles/ion in the solution
what are strong acid pH’s
a solution with a pH of 3 or less is considered a strong acid
what are strong base pH’s
a solution with a pH of 10 or higher is considered to be a strong base
what pH does the universal indicator cover
0 to 14
indicators accuracy and precision
low accuracy and low precision
indicators can only approximate pH range and the estimated pH of a given solution may differ greatly between trials
calibrated pH meters accuracy and precision
high accuracy and high precision
what is the accuracy of most pH meters
+-0.01 pH units
What are the three types of indicators
1)natural indicators
2)Commercial indicators
3)pH meters
What is a pH meter
and what does it measure, and how does it measure it.
-pH meter=
instrument= measures acidity or alkalinity in a solution
-pH meter does
this by reading the hydrogen ion concentration in the solution
What is precision
and what is accuracy.
-precision and
accuracy=two ways to describe results when completing a process that is
repeated=
-precision=yield
results that are close to each other repeatedly
-accuracy=yield
results being close to the accepted or true value of the test.
Colour or
universal indicator across pH
Imagine it as a
rainbow, with pH of 7 showing green. Anything less then pH 7 changes
substance colour towards red, and any pH more than 7 changes substance colour
towards purple.
