What is the mass number in this atom:
The top number: 23
What is the atomic number in this atom:
The bottom number: 11
What is the relative mass of a proton?
What is the relative mass on a neutron?
What is the relative mass on an electron?
What is the mass number?
The total number of protons and neutrons in an atom
What is the name for atoms of the same element can have different numbers of neutrons?
Isotopes of that element
What does the relative atomic mass of an element compare the mass of atoms of the element with?
The Carbon 12 isotope. it is an average value for the isotopes of the element
What is the relative formula mass of a compound?
The sum of the relative atomic masses of the atoms in the numbers shown in the formula
The is the relative formula mass of a substance, in grams, known as?
One mole of that substance
What is the relative atomic mass of an element?
The mass number of an element
How can elements and compounds be detected?
Using instrumental methods
What are instrumental methods often?
Accurate, sensitive, rapid and are particularly useful when the amount of a sample is very small
How can artificial colours be detected and identified in foods?
What should be used to draw the baseline on filter paper and why?
A pencil because pen ink would run with the water
What are examples of instrumental methods?
Gas chromatography and mass spectroscopy
What does gas chromatography allow?
The separation of a mixture of different compounds
What can the time taken for a substance to travel through the column be used for?
Identifying the substance
What happens in a gas chromatography column?
Different substances, carried by gas, travel through a column packed with solid material at different speeds so that they become separated
What do the different peaks on a gas chromatograph show?
The number of compounds present
What do the position of the peak on a gas chromatograph show?
The retention time
What can a mass spectrometer do?
Identify substances vert quickly and accurately and can detect very small quantities
What is the molecular mass given by?
The molecular ion peak
What can the mass spectrometer also give us?
The relative molecular mass of each of the substances separated in the column
What is the retention time?
The time taken to reach the detector
How can the percentage of an element in a compounds be calculated?
Relative atomic mass x number of atoms in that element
divided by /
The relative formula mass of the entire compound
times by x
What is the first step for calculating the empirical formula?
List all the elements in the compound
What is the second step for calculating the empirical formula?
Underneath, write their masses or percentages given to you
What is the third step for calculating the empirical formula?
Divide each mass or percentage by the relative atomic mass for that particular element
What is the fourth step for calculating the empirical formula?
Turn the numbers into a nice and simple ratio by multiplying/dividing by a nice number like 10
What is the fifth step for calculating the empirical formula?
Get the ration into its simplest form, this then tells you which numbers should follow each element giving you the empirical formula
What is the first step in calculating the masses of reactants and products from a reaction?
Write out the balanced symbol equation
What is the second step in calculating the masses of reactants and products from a reaction?
Work out the relative formula mass for the two bits you need
What is the third step in calculating the masses of reactants and products from a reaction?
Apply the rule divide to get one, then multiply to get all
Why is it not possible to obtain the calculated amount exactly?
Although no atoms are gained or lost, it is possible not to gain the full amount because: the reaction may be reversible, some product may be lost when removed from the reaction mixture (e.g. filtering) and sometimes other reactions occur which use up the reactants
How do you calculate the percentage yield?
actual yield (grams) / x 100 predicted yield (grams)
What is a reversible reaction?
One where the products of the reaction can themselves react to produce the original reactants
How can reversible reactions be represented?
With an arrow