AS-level AQA Chemistry

What is the charge of a proton?

+1

What is the charge of a neutron?

0

What is the charge of an electron?

-1

What is the mass of a proton?

1

What is the mass of a neutron?

1

What is the mass of an electron?

1/1800

What is an isotope?

Isotopes of an element are atoms with the same number of protons but different numbers of neutrons.

Why do isotopes of an element all have the same chemical properties?

This is because chemical properties are decided by the number and arrangements of electrons and all isotopes of an element have the same number of electrons.

Why do isotopes of an element have different physical properties?

This is because physical properties are decided by the mass number and isotopes of an element have different mass numbers.

What is the first stage in time of flight mass spectrometry and what are the 2 ways it can occur?

1. Electron spray ionisation

2.Electron impact ionisation

What is electron spray ionisation?

The sample is dissolved and pushed through a small nozzle at high pressure. A high voltage is applied to it causing each particle to gain a + ion so that the gas is made up of positive ions.

What is electron impact ionisation?

The sample is vaporised and an electron gun is used to fire high energy electrons which knocks of 1 electron of each particle so they become positive ions.

What is the second stage in time of flight mass spectrometry?

Acceleration

What happens in the acceleration stage of time of flight mass spectrometry?

The positively charged ions are accelerated by an electric field so that they all have the same kinetic energy which means that the lighter ions will move faster than the heavier ions.

What is the third stage in time of flight mass spectrometry?

Ion drift

What happens in the ion drift stage of time of flight mass spectrometry?

The ions enter a region with no electric field, so they just drift through it. Lighter ions will drift through faster than heavier ions.

What is the final stage of time of flight mass spectrometry?

Detection

What happens in the detection stage of time of flight mass spectrometry?

Because ions have a lower mass/charge ratio travel at a higher speed in the drift region, they reach the detector in less time than ions with a higher mass/charge ratio. The detector detects charged particles and a mass spectrum is produced.

What is the electronic configuration of calcium?

1s2,2s2,2p6,3s2,3p6,4s2

What is the electronic configuration of chromium?

1s2,2s2,2p6,3s2,3p6,3d5,4s1

What is the first ionisation energy?

The first ionisation energy needed to remove one electron from each atom in 1 mole of gaseous atoms to form 1 mole of +1 gaseous ion..

How does nuclear charge affect ionisation energy?

More protons means more positively charged means the stronger the attraction for electrons.

How does distance from the nucleus affect ionisation energy?

The closer the electron is to the nucleus, the stronger the attraction.

How does shielding affect ionisation energy?

As the number of electrons between outer electrons and the nucleus increases, the outer electron feels less attraction towards the nuclear charge.

What is the trend in ionisation energy down a group?

The first ionisation energy down a group has a general decrease because down a group each element has an extra electron shell compared to the one above so the extra inner shells will shield the outer electrons from the nucleus attraction.

What is the trend in ionisation energy across a period?

The first ionisation energy across a period has a general increase because it gets harder to remove outer shell electrons.

What is the definition of relative atomic mass (Ar)?

The relative atomic mass is the average mass of an atom of an element on a scale where an atom of carbon-12 is 12.

What is the definition of relative molecular mass (Mr)?

The relative molecular mass is the average mass of a molecule on a scale where an atom of carbon-12 is 12.

What is the Avogadros Constant?

The number of particles in a mole which is equivalent to 6.02 x 10^23.

What is an equation for number of moles involving mass and Mr?

number of moles = mass / Mr

What is an equation for number of moles involving concentration and volume?

number of moles = concentration x volume

What is an equation for number of particles involving number of moles and Avogadros constant?

number of particles = number of moles x Avogadros constant

What is the Ideal Gas Equation?

PV = nRT

What is P in regards to the Ideal Gas Equation and what is its units?

P = nRT / V

pressure and is measured in Pa or Pascals

What is V in regards to the Ideal Gas Equation and what is its units?

V = nRT / P

volume and is measured in m^3

What is n in regards to the Ideal Gas Equation?

n = PV / RT

number of moles

What is R in regards to the Ideal Gas Equation?

R = 8.31K^-1mol^-1

gas constant

What is T in regards to the Ideal Gas Equation?

T = temperature and is measured in K or kelvin ( 273 + Celsius)

How do you work out empirical formula?

1.mass / Mr

2.divide by the smallest number

3.ratio

How do you work out molecular formula?

1.find total mass

2.mass / Mr

3.multiply answer by empirical formula

What is the equation for percentage atom economy?

atom economy % = mass of desired product / total mass of reactants x 100

Why are high atom economy processes better?

They produce less waste and make more efficient use of raw materials so are less expensive.

How do you convert m^3 into dm^3?

x1000

How do you convert dm^3 into cm^3?

x1000

How do you convert cm^3 into dm^3?

/1000

How do you convert dm^3 into m^3?

/1000

What is ionic bonding?

The electrostatic attraction between oppositely charged ions in a lattice.

When are ions formed?

When one or more electrons are transferred from one atom to another.

What is the charge on a sulfate ion (SO4)?

2-

What is the charge on a hydroxide ion (OH)?

-

What is the charge on a nitrate ion (NO3)?

-

What is the charge on a carbonate ion (CO3)?

2-

What is the charge on an ammonium ion (NH4)?

+

What are ionic compounds made up of?

A positively charged and negatively charged part.

What is the overall charge of a compound?

0 (neutral)

What is covalent bonding?

A shared pair of electrons where molecules are held together by strong covalent bonds.

What is metallic bonding?

The attraction between delocalised electrons and positive ions arranged in a lattice.

What is an ionic crystal structure?

A lattice of positive ions each surrounded in a regular arrangement by negative ions with strong ionic bonds between them so a lot of energy is needed to break them.

What is the structure of a sodium chloride compound?

Ionic crystal structure.

What are ions?

Charged particles.

When can ions conduct electricity?

When liquid or molten because the ions are free to move.

Why are metals ductile and malleable?

There are no direct bonds between metal ions so they can slide over each other.

What is a giant metallic structure?

A regular lattice of positively charged metal ions held by a cloud of delocalised electrons.

Why do giant metallic structures have a high melting point?

Because of strong metallic bonds.

What is the structure of the magnesium?

Giant metallic structure.

What is a macromolecular structure?

One in which large numbers of atoms are linked into a regular 3D arrangement by covalent bonds.

Why do macromolecular structures have high melting points?

Strong covalent bonds.

What is the structure of graphite?

Macromolecular: strong covalent bonds hold layers together. weak forces had layers.

What is the structure of diamond?

Macromolecular with a tetrahedral shape.

What is the structure of silicon dioxide?

Macromolecular or giant covalent structure.

What is a simple molecular structure?

Small grouped atoms strongly held together by covalent bonding with weak intermolecular forces between molecules.

Why do simple molecular structures have low melting points?

weak van der waal forces.

Why do simple molecular structures not conduct electricity?

They have no free energy carriers.

What is a charge cloud?

An area where electrons whizz around inside the charge cloud.

What exist as charge clouds?

Bond pairs and lone pairs of electrons exist as charge clouds.

Why do charge clouds repel each other?

Electrons are all-charged so the charge clouds will repel each other as much as possible so the electron pairs in the outer electron will sit as far apart as possible.

What are the biggest pair-pair ratio angles?

Lone pair to lone pair.

What are the second biggest pair-pair ratio angles?

Lone pair to bond pair.

What are the smallest pair-pair ratio angles?

Bond pair to bond pair.

What is electron pair repulsion theory?

The shape adopted is the one which keeps repulsive forces at a minimum.

What is the shape and bond angles of a compound with 2 bond pairs?

Linear and 180 degrees.

What is the shape of BeCl2?

Linear

What is the shape and bond angles of a compound with 3 bond pairs?

Triganol planar and 120 degrees.

What is the shape and bond angles of a compound with 4 bond pairs?

Tetrahedral and 109.5 degrees.

What is the shape and bond angles of a compound with 5 bond pairs?

triganol bipyramidal and either 120 degrees or 90 degrees.

What is the shape and bond angles of a compound with 6 bond pairs?`

Octahedral and 90 degrees.

What is the shape of BF3?

Triganol planar.

What is the shape of CH4?

Tetrahedral.

What is the shape of PF5?

Triganol bipyramidal.

What is the shape of SF6?

Octahedral

What is the shape and what are the bond angles reduced from and to in a structure with 3 bond pairs and 1 lone pair?

Pyramidal and the angles are reduced from 109.5 to 107 degrees.

What is the shape and what are the bond angles reduced from and to in a structure with 2 bond pairs and 2 lone pairs?

Bent and the angles are reduced from 109.5 to 104.5 degrees.

What is the shape of ammonia and why?

Pyramidal because it has 3 bond pairs and 1 lone pair.

What is the shape of water and why?

Bent because it has 2 bond pairs and 2 lone pairs.

What is the shape of carbon dioxide and why?

Linear because it has 2 bond pairs and no lone pairs.

What is different about negative ions?

They have one extra electron in the outer shell.

What is different about positive ions?

They have one less electron in the outer shell.

What is electronegativity?

An atoms ability to attract the electron pair in a covalent bond.

What causes a dipole?

A difference in charge between 2 atoms caused by a shift in electron density in the bond.

What is the relationship between polarity and electronegativity?

The greater the difference in electronegativity, the more polar the bond.