Atomic structure and analysis Flashcards
What is the relative masses of the subatomic particles?
Proton = 1 Neutron = 1 Electron = very small
Whats the mass number?
The mass number of an atom is the total number of protons and neutrons it contains.
Whats the atomic number of an atom?
The number of protons it contains.
What are isotopes?
Atoms of the same element with different numbers of neutrons are called isotopes.
How do you work out the relative formula mass of a substance?
To find the relative formula mass of a substance, you just add together the relative atomic mass values for all the atoms in its formula.
What is one mole of a substance?
The relative formula mass of a substance - shown in grams
What is the relative atomic mass of an element?
Its an average value for the isotopes of the element
What is paper chromatography used to analyse?
Paper chromatography is used to analyse coloured substances, such as the coloured pigments in plants and artificial colours used as food additives.
Why do some substances travel further up in paper chromatography?
Some of the coloured substances are better at dissolving in the liquid than they are at bonding with the paper, so they travel further up the paper.
Why are instrumental methods of analysis good?
Fast
Accurate (they reliably identify elements and compounds)
Sensitive (they can detect very small amounts of a substance in a small amount of sample)
Explain the method of gas chromatography.
The sample is dissolved in a solvent, then injected into one end of the column.
An unreactive gas - usually nitrogen - carries the sample through the column.
Different substances in the sample travel through the column at different speeds and so become separated from each other.
The separated substances leave the column one after the other. As they leave, they are detected by a detector.
What is retention time in gas chromatography?
The time taken for a substance to travel through the column
What does a mass spectrometer do and why is it useful?
It can identify substances very quickly and accurately and in very small amounts.
Explain the graph produced in gas chromatography?
The number of peaks shows the number of compounds present in the sample.
The position of each peak shows the retention time for each compound.
What is the conservation of mass?
The total mass of products at the end of the reaction is equal to the total mass of the reactants at the beginning.
