Chemical Analysis (8) Flashcards
What is a pure substance?
A pure substance is a single element or compound, not mixed with any other
substance
What is a formulation and how is it made?
A formulation is a mixture of compounds in measured quantities that has been
designed as a useful product.
What is an example of formulations
Formulations include fuels, cleaning agents, paints, medicines, alloys,
fertilisers and foods.
E.g. alloys are mixtures of metals; they are harder than pure metals, so have
a particular purpose.
Describe paper chromatography in steps
(1)
A start line is drawn near the bottom of the paper. The mixture is spotted on the line.
Describe paper chromatography in steps
(2)
A beaker is filled with small amount of solvent (it cannot touch or go above the start line
when paper is placed in a beaker)
Describe paper chromatography in steps
(3)
Paper is hung on a rod and placed in a beaker.
Describe paper chromatography in steps
(4)
Solvent travels up the paper, thus separating the components.
Describe paper chromatography in steps
(4)
Before solvent level reaches the end, the paper is taken out and the finish line is
marked. The paper is dried.
Describe paper chromatography in steps
(5)
The procedure works when different compounds have different affinities for the
solvent/paper. Stronger attraction for the paper - travels slowly with the solvent etc.
Describe paper chromatography in steps
(6)
Paper is called the stationary phase - it doesn’t move. Solvent is the mobile phase.
How is R(small f)calculated?
Distance moved by the spot / distance moved by solvent
In a paper chromatography experiment,
a compound A was found to have an Rf
value of 0.85 - what does it tell you about
the compound?
It has a higher affinity for the solvent than for the paper.
Describe the tests for hydrogen
Hydrogen – pop with burning splint over gas
Describe the tests for oxygen
Oxygen – glowing splint relights
Describe the tests for carbon dioxide
Carbon dioxide – turns limewater (Ca(OH)2) milky
Describe the tests for chlorine
Chlorine – bleaches damp litmus paper and makes it white
Describe the flame test results
Lithium compounds– crimson red flame
Describe the flame test results
Sodium compounds - yellow flame
Describe the flame test results
Potassium compounds - lilac flame
Describe the flame test results
Calcium compounds – orange red flame
Describe the flame test results
Copper compounds -green flame.
Describe the sodium hydroxide test results and write the equations
Describe the test for carbonate anions
Describe the test for sulfate anions
Describe the test for halide
anions
What are instrumental
methods?
They are accurate, sensitive and rapid methods which are useful when the amount
of sample is very small
Describe the flame emission spectroscopy
Step 1
instrumental method used for identifying metal ions in solution or measuring their concentration
Describe the flame emission spectroscopy
(Step 2)
Spectroscope measures the exact wavelength of the light emitted by a metal
ion
Describe the flame emission spectroscopy
(Step 3)
That allows for definite identification - sometimes colours are difficult to
distinguish.
Describe the flame emission spectroscopy
(Step4)
Concentrations are found by measuring the intensity of light emitted. The
more intense light, the greater the concentration of the metal ion in a solution.
Describe the flame emission spectroscopy
(Step 5)
From the intensity vs concentration graph, you can read off a relevant
concentration value at a given intensity.
What are cations and anions?
Cations are the positive ions; anions are the negative ions.
