Chemistry EOYS

Atomic number

the number of protons in the nucleus of an atom

Isotopes

Atoms of the same element that have different numbers of neutrons

Carbon 12

Most common isotope of Carbon

Relative isotopic mass

The mass of an atom of an isotope compared with one-twelfth of the mass of an atom of carbon-12.

Relative atomic mass

The weighted mean mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12.

What is a mass spectrometer?

A machine used to analyse elements or compounds and finds the percentage abundances of the isotopes in a sample of an element

What does the weighted mean mass mean?

The percentage abundance of each isotope and the relative isotopic mass of each isotope.

What is the basic principle of the mass spectrometer?

1. A sample is placed in the spectrometer
2. The sample is vaporized and then ionized to form positive ions.
3. Ions are accelerated. Heavier ions are harder to deflect so the ions of each isotope is separated.
4. Ions are then detected on a mass spectrometer

Why are heavier atoms harder to deflect in mass spectroscopy?

The ions are accelerated so that they all have the same kinetic energy. The ions are then deflected by a magnetic field according to their masses. The lighter they are, the more they are deflected.

What are the units of mass spectrometer?

mass to charge ratio m/z

What is mass to charge ratio equal to?

Relative mass of ion/relative charge on ions

How do you work out relative atomic mass?

Sum of (isotope abundance x isotope mass number) / sum of abundances of all the isotopes

What are the 3 things deflection are affected by?

Amount of energy a particle has, mass of particle and the charge of it

Mass of particle

Less mass, more deflections

Charge of particle

More charge, more deflection

Explain the 1st step of mass spectrometry

Vaporization to form gaseous atoms

Explain the 2nd step of mass spectrometry

Ionisation - The gaseous atoms enter the ionisation chamber and are bombarded by high energy electrons from the electron guns. It breaks chains and mainly single positive ions are formed

Explain the 3rd step of mass spectrometry

Acceleration - Beam of positively charged electrode and focused using stilts. After they will all have the same kinetic energy

Explain the 4th step of mass spectrometry

Deflection - Beam of positive ions passes through magnetic field. The less mass or greater the charge of the ion, the more it is deflected by the field

Explain the 5th step of mass spectrometry

Detection - The detector uses n electrical field to detect the charge ions and measure the relative abundance of the ion.

Which ions are detected first?

Lighter ions are detected first as they have a shorter drift time compared to heavier ions so they are separated by mass

How does the magnetic field work?

The positively charged ions in the sample are accelerated by an electrical field. A negatively charge acceleration plate attracts the positive ions on the back

Binary compound

A compound composed of two elements

What do binary compound end in?

-ide

What is a mole?

amount of substance

The Avogadro constant

6.02 x 10^23

Molar mass

the mass of one mole of a pure substance

What are the units of molar mass?

g/mol

What is equation for the amount of substance/moles?

moles \= mass/molar mass

What is the empirical formula?

The simplest whole number ratio of atoms of each element in a compound

Water of crystallisation

Water molecules that form an essential part of the crystalline structure of a compound

What is 1cm^3 equal to?

1 ml

What is 1dm^3 in cm^3?

1000cm^3

What is 1dm3 equal to?

1 litre

What is the equation for moles using volume?

moles \= concentration x volume

Molar gas volume

The volume per mole of gas molecules at a stated temperature and pressure

What is the molar gas volume at RTP?

24 dm^3^-1

What is equation for mole using molar gas volume?

moles \= volume / molar gas volume

What is the ideal gas equation?

PV\=nRT

What is a strong acid?

An acid which completely splits up into its ions in water. E.g. when HCl is in water all the HCl molecules split up into H⁺ and Cl⁻

What is a weak acid?

An acid which will have some molecules which do not split up into their ions. E.g. in ethanoic acid only some of the molecules will have split up into the ethanoate ion and H⁺ ions.

What is a base?

A substance that reduces the hydrogen ion concentration of a solution which neutralizes an acid to form a salt

What is an alkali?

A soluble base that releases OH- ions in solution

What is neutralization?

acid + base \= salt + water

What is the formula for sulfuric acid?

H2SO4

What is the formula for nitric acid?

HNO3

What is the formula for ethanoic acid?

CH3COOH

What is the reaction of a metal oxide and an acid

salt + water

What is the reaction of a metal carbonate and an acid?

Salt + water + carbon dioxide

What is titration?

the process of adding a known amount of solution of known concentration to determine the concentration of another solution

What is titration used for?

to determine the concentrations of an unknown acid or base using a standard solution

How do you do a titration?

-Measure a set volume of alkali into a flask
-Line the burette with an acid of known concentration, then fill the burette with the same acid
-Slowly add the acid to the flask, making sure to swirl it at regular intervals
-When the solution changes colour, measure the volume of acid used
-To get a pure solution, repeat this process with no indicator

How do you prepare a standard solution?

- Weigh out the correct mass of solid in a beaker.
- Add water and stir and dissolve.
- Transfer to standard flask and rinse beaker.
- Invert the flask to mix.

What is an oxidation number?

The charge an atom has after it has gained/lost electrons during an ionic bond

What is the oxidation number for elements?

always 0

What is the oxidation number for an oxygen compound?

-2

What is the oxidation number for a hydrogen compound?

+1

What is the oxidation number for a fluorine compound?

-1

What is the oxidation number for a sodium and potassium compound?

+1

What is the oxidation number for a magnesium or calcium compound?

+2

What is the oxidation number for a chlorine or bromine or iodine compound?

-1

What are the special cases for oxidation numbers?

Hydrogen in metal hydrides \= -1
Oxygen in peroxides \= -1
Oxygen bonded to Fluorine \= +2

What do roman numerals represent?

Ions with different charges, it shows the oxidation number

What is oxidation?

loss of electrons, gain of oxygen, increase in oxidation number and loss of hydrogen

What is reduction?

gain of electrons, loss of oxygen, decrease in oxidation number and gain of hydrogen

What is a redox reaction?

transfer of one or more electrons from one reactant to another

What are shells?

Orbitals within the main energy level

The principle quantum number,n

-describes orbital energy level and the size
-always a positive whole number
-the higher the n value, the higher the energy level and the larger the orbital
-the probability of finding an electron far from the nucleus is higher

1st ionization energy

The energy required to remove an electron from each atom in one mole of gaseous atoms of an element to form one of gaseous 1+ ions

2nd ionization energy

Energy needed to remove one electron from each 1+ ions in one mole of gaseous 1+ ions of an element to form one mole of gaseous 2+ ions

How do you draw ionisation energy?

Draw the graph in opposite order
e.g nitrogen (2,5) is drawn as (5,2)

What are the factors affecting ionization energy?

Atomic radius, nuclear charge and electron shielding

Atomic radius

The greater the distance from the nucleus to the outer electrons, the less the attraction

Nuclear charge

The more protons there are in the nucleus, the more positively charged the nucleus is and the stronger the attraction for the electrons

Electron Shielding

Inner shell electrons can repel outer shell electrons. The repulsion reduces the attraction between the nucleus and the outer electrons

Why does the variation of the ionisation energy of Group 2 decreases going down the group?

Since the atomic radius increases, the nuclear charge and shielding also increases

What happens when you go along period?

The ionisation energy increases as the atomic radius decreases. Nucleus charge increases while shielding stays the same

What id the max number of electrons equation?

2n^2

What are atomic orbitals?

A region around the nucleus that can hold up to two electrons with opposite spins

What happens when there is no empty orbitals?

They pair up

What are the different types of orbitals?

s, p, d, f

S-orbitals

Spherical, it can hold 1 or 2 electrons

P-orbitals

They are dumbbell shaped and can also hold 1 or 2 electrons. There are 3 separate p-orbitals at right angles to each other

How many orbitals are in each shell from n \= 2

3 orbitals

The greater the shell number is....

the further the p-orbital is from the nucleus

What are the max amount of electron in s sub level?

2

What are the max amount of electron in p sub level?

6

What are the max amount of electron in d sub level?

10

What are the max amount of electron in f sub level?

14

What are the sub shells in order?

1s2, 2s2, 2p6, 3s2, 3s6, 4s2, 3d6, 4p6, 4d10, 4f14

How many electrons are there in the 1st shell?

2

How many electrons are there in the 2nd shell?

8

How many electrons are there in the 3rd shell?

18

How many electrons are there in the 4th shell?

32

What are orbitals?

Regions of space that electrons are likely to be in

What is lost first for ions?

The electrons in the highest energy levels are lost first, but when losing electrons, electrons are lost from 4s before 3d.

Ionic Bonding

The electrostatic attraction between oppositely charged ions. It holds together cations and anions in ionic compounds

Giant ionic lattice

A three-dimensional structure of oppositely charged ions, bonded together by strong ionic bonds.

ionic melting/boiling point

Very high since it provides the large quantity of energy needed to overcome the strong electrostatic attraction between the ion

ionic solubility

Many ionic compounds dissolve in polar compounds. Polar water molecules break down the lattice and surround each ion in solution.