CH1.3 CHemical calcuations

Question 1

realtive atomic mass

Answer 1

is the average mass of one atom of the elements relative to one-twelth the mass of one atom of carbon-12

Question 2

relative isootopic mass

Answer 2

is the mass of an atom of an isotope relative to one-twelth the mass of an atom of carbon-12

Question 3

relative formula mass

Answer 3

is the average mass of a molecule relative to one-twelfth the mass of an atom of carbon-12

Question 4

what does the mass spec measure when it is calculating hte realative atomic mass

Answer 4

The mass of each different isotope of the elements and the relative abundance of each isotope of the element

Question 5

what are the name of the four main steps of the mass spec

Answer 5

Ionisation, Acceleration ,Defelction, Detection

In Antartica Dont Dive

Question 6

exsplain the ionisation step of the mass spec

Answer 6

The vaporised sample passes into the ionisation chamber, The particle in the sample (atoms or molecuels) are therefore bombarded with a stream of electrons, and some of the collisions are sufficiently energetic to knock one or more electron out of the sample particles to make positive ions.

Question 7

what is the most common ion to make during the ionisation step of the mass spec and why

Answer 7

+1 ions because it is much more difficult to remove furthre electrons from already positive ions.

Question 8

accelerations step of the mass spec exsplained

Answer 8

an electric field accelerated the postive ions to high speed

Question 9

deflection step of the mass spec exsplained

Answer 9

different ions are deflected by the magnetic field by different amount depending on the mass of the ions (lighter ions are deflected more) and by the charge on the ion (higher the charge the more its defelcted)

(mass charge ratio )

Question 10

detection part of the mass spec exsplained

Answer 10

the beam of ions pasing through the machine is deteced electrically. Only ions with the correct mass/charge ratio make it right through the machine to the ion detector. (The other ions collide with the walls where they will be pick up electrons and will be neutralied. Eventually they get removed from the mass spectrometer by the vacuum pump.) The signal is then amplified and recoreded.

Question 11

what are the conditions needed in a mass spec and why

Answer 11

there must be a vacuum so that the ions do not hit any other molecules such as that of air

Question 12

uses of the mass spec (3)

Answer 12

• identifying unkown compounds e.g.testing athleted for prohibited drugs
• identifying trace compounds in forensic science
• analysing molecules in space

Question 13

why do you get lots of lines on the mass spec graph

Answer 13

the molecular ions are energetically unstable, and some of them will break up into smaller pieeces or fragments, all sorts of fragmentations of the original molecular ion are possible and that means that you will get a wide range of lines in the mass spectrurm

Question 14

one mole

Answer 14

is amount of any substance that conatain the same number of particles as there are atom in exactly 12g of carbon-12

Question 15

The Avogadro constant

Answer 15

is the number of atoms per mole

Question 16

Molar mass

Answer 16

is the mass of one mole of a substance

Question 17

moles mass mr triangel equations

Answer 17

moles = mass/Mr

Question 18

moles, concentration, volume triangle equations

Answer 18

moles = concentration X volume

Question 19

Stoichiometry

Answer 19

is the molar realtionship between the amounts of reactants and products in a chemical reaction

Question 20

Empirical formula

Answer 20

Is the simplest formula showing the simplest whole number ratio of the amount of elements present

Question 21

molecular formula

Answer 21

Shows the actual number of atoms of each element present in the molecule. It is a simple multiple of the empirical formula

Question 22

molecular volumes

Answer 22

is the volume per mole of gas ((it will always be given in a question)

Question 23

three laws involving gases

Answer 23

Boyles Law , charles Law, and Avogadro’s principle

Question 24

Boyles law

Answer 24

at constant temperature, the volume of a fixed mass of gas is inversely proportional to its pressure

Question 25

Charles law

Answer 25

The volume of a fixed mass of a given gas at constant pressure is directly proportional to its temperature in kelvin

Question 26

Avogadros principles

Answer 26

Equal volumes of different gases, measured at the smae temperature and pressure, contain the same number of molecules.