c12 chemical analysis Flashcards
What is a pure substance?
A pure substance is one that is made up of just one substance.
That substance can be either an element or a compound.
What are the fixed points?
The melting and boiling points of an element or a compound
What are formulations?
useful mixtures,
made up in definite proportions,
designed to giveaproduct the best
properties possible to carry out its
function.
What is an impure substance?
is a mixture of two or more different elements or compounds.
What are the 2 main phases of chromatography
Mobile phase – The solvent or gas that carries the mixture through the stationary phase.
Stationary phase – The solid or liquid material that remains fixed and interacts with the components of the mixture.
What is the Rf value
The Rf value (Retention Factor) is the ratio of the distance traveled by a component to the distance traveled by the solvent front. It is used to identify components in a mixture
Rf=Distance moved by substance/distance moved by solvent
What is chromatography used for in identifying unknown compounds?
Chromatography is used to separate and identify mixtures of compounds, such as amino acids, by analyzing their interactions with the mobile and stationary phases.
What does a single spot on a chromatogram indicate?
A single spot suggests that the sample might be a pure substance.
What does multiple spots on a chromatogram indicate?
Multiple spots indicate that the sample is likely a mixture of different compounds.
What is a positive test for hydrogen gas being a product of the reaction?
Hydrogen gas burns rapidly with
a ‘pop’ when you apply a lighted
splint.
What is a positive test for oxygen gas being a product of the reaction?
relights a glowing splint.
What is a positive test for carbon dioxide gas being a product of the reaction?
When bubbled into limewater through a delivery tube, the limewater turns cloudy
What is a positive test for chlorine gas being a product of the reaction?
damp blue litmus paper turns white (as it gets bleached)
What is a flame test used for?
A flame test is used to identify the presence of certain metal ions in a compound based on the characteristic color they emit when heated in a flame.
What causes the colour in a flame test?
The colour is caused by electrons in the metal ions being excited to higher energy levels by the heat and then emitting light of specific wavelengths as they return to their ground state.
What colour does sodium (Na) produce in a flame test?
Sodium produces a bright yellow flame.
What colour does potassium (K) produce in a flame test?
Potassium produces a lilac or pale violet flame.
What colour does calcium (Ca) produce in a flame test?
Calcium produces an orange-red flame.
What colour does copper (Cu) produce in a flame test?
Copper produces a blue-green flame.
What colour does lithium (Li) produce in a flame test?
Lithium produces a crimson or red flame.
What colour does barium (Ba) produce in a flame test?
Barium produces a green flame.
What colour does strontium (Sr) produce in a flame test?
Strontium produces a red flame.
Why is a platinum or nichrome wire often used in flame tests?
Platinum or nichrome wire is used because it does not produce a colour in the flame, ensuring that the observed colour is solely due to the metal ion being tested.
How can you test if a substance is a carbonate?
Add a dilute acid to the substance. If it fizzes and produces carbon dioxide gas, it is a carbonate. Repeat the carbon dioxide test to find whether it is a carbon dioxide acid being released.
How can you test for the presence of halide ions (chloride, bromide, iodide) in a compound?
Add dilute nitric acid followed by silver nitrate solution. A precipitate indicates the presence of halide ions
What does the colours of the precipitate tell?
iodide ions, I-, give a yellow precipitate.
bromide ions, Br-, give a cream precipitate
chloride ions, Cl-, give a white precipitate
How can you test if a substance is a sulfate?
You identify sulfates by adding hydrochloric acid, then barium chloride solution. This produces a white precipitate.
What are the benefits of modern instrumental methods in chemical analysis?
Highly accurate and sensitive
Quicker
Enable analysis of very small samples
What are the disadvantages of using instrumental methods?
Equipment is usually very expensive
Requires special training to use
Results often need comparison with known substances for interpretation
What is flame emission spectroscopy used for?
Flame emission spectroscopy is used to analyse samples for metal ions by heating the sample in a flame and analysing the light emitted.
How does flame emission spectroscopy work?
The sample is heated in a flame, exciting electrons in metal ions. When these electrons return to lower energy levels, they emit light. The wavelengths of this light are analysed to identify the metal ions.
How can the concentration of metal ions in a sample be determined using flame emission spectroscopy?
The intensity (or absorbance) of light at specific wavelengths characteristic of a metal ion is measured. The spectrometer is calibrated with solutions of known concentrations to determine the unknown concentration.
How is flame emission spectroscopy used in the steel industry?
It is used to control the amounts of trace metals in steel, as the quality of steel depends on the precise composition of these metals.
What is the significance of the line spectrum in flame emission spectroscopy?
The line spectrum is unique to each metal ion and is used to identify the ion by comparing it with known spectra in a database.
