Atomic structure and quantitative chemistry Flashcards
For an atom on the periodic table, what does the larger number represent?
The mass number; the number of protons plus neutrons.
For an atom on the periodic table, what does the smaller number represent?
The atomic number; the number of protons.
What is the relative atomic mass of a proton?
1.
What is the relative atomic mass of a electron?
Very small (1/2000).
What is the relative atomic mass of a neutron?
1.
Atoms of the same elements with different numbers of neutrons are known as what?
Isotopes.
The relative atomic mass of an atom of an element is relative to what?
The 12^C atom.
The relative atomic mass displayed on a periodic table is an average of what?
An average of the relative atomic mass for the isotopes of that element.
Relative formula mass of a compound is what?
The relative atomic masses of all the atoms in the compound combined.
The relative formula mass of a substance in grams is known as what?
A mole of that substance.
Elements and compounds can be detected accurately by using what type of methods?
Instrumental methods.
Advantages of using instrumental methods:
Accurate.
Sensitive.
Rapid.
Small samples required.
An example of a use of chemical analysis.
Eg: identifying additives in food.
Artificial colours in foods can be detected and identified by what method?
Paper chromatography.
Gas chromatography (GC) can be linked to what to help identify substances?
A mass spectrometer making GC-MS a method of identifying substances.
How does GC-MS work?
Gas chromatography allows for the separation of a mixture of compounds.
The time taken for a substance to travel through the column can be used to help identify the substance.
The output of the GC can be linked to a MS which can be used to identify the substance.
MS can also give the relative molecular mass of each substance in the column.
Molecular ion peaks on a graph from a MS show what?
The relative molecular mass of the substance.
Number of peaks on a GC graph show what?
The number of substances present.
Position of a peak on a GC graph shows what?
Retention time of the substance which can be used to identify the substance as different substances have different retention times.
The percentage of an element in a compound can be calculated how?
RFM of compound/RAM(RFM) of element x100
Empirical formula of a compound can be found how?
Find the mass of each reactant. Find the molar mass of each. Find the number of moles for each. Then do the amount for each divided by the smallest amount out of each of them. Left with a ratio.
What is empirical formula?
The simplest whole number ratio of elements in a compound. This can be the same as the actual number of atoms but not always.
How do you calculate masses of reagents/products?
E - check it is a balanced equation.
M - calculate moles of substance you know.
R - find reacting ratio of two things in question.
M - find mass of unknown in grams.
True or false, in a chemical reaction atoms can be gained or lost.
False, in a chemical reaction atoms can neither be created nor destroyed, they may however be used in another chemical reaction at the same time.
