Physical I

Question 1

What is relative atomic mass?

Answer 1

the average mass of an atom of an element compared to 1/12 the mass of an atom of carbon-12

Question 2

What does a mass spectrometer give?

Answer 2

gives accurate information about relative isotopic mass and also about the relative abundance of isotopes

Question 3

What is electron impact ionisation?

Answer 3

sample is vaporised, electron gun fires high energy electrons at it, causing an electron to be knocked off each particle to produce 1+ ions

Question 4

What is electrospray ionisation?

Answer 4

sample is dissolved and pushed through a fine needle with a high voltage tip, each particle gains an H+ ion and turns into a gas

Question 5

First ionisation energy

Answer 5

the energy required to remove the most loosely held electron from one mole of neutral gaseous atoms to produce 1 mole of gaseous ions each with a charge of 1+.

Question 6

What are the stages of TOF spectrometry?

Answer 6

ionisation, acceleration, ion drift, ion detection

Question 7

Acceleration

Answer 7

positively charged ions are accelerated by an electric field so that they have the same kinetic energy

Question 8

Ion drift

Answer 8

ions enter a region with no electric field so they drift through it. lighter ions drift faster

Question 9

Ion detection

Answer 9

negatively charged plates detects charged particles and a mass spectrum is produced

Question 10

Relative molecular mass

Answer 10

the average mass of one molecule of an element or compound compared to 1/12th the mass of an atom of carbon-12

Question 11

co-ordinate bond (dative covalent)

Answer 11

bond contains a shared pair of electrons with both electrons supplied by one atom

Question 12

What is a dipole?

Answer 12

difference in charge between the two atoms of a covalent bond

Question 13

What is a dipole caused by?

Answer 13

a shift in electron density in the bond due to the electronegativity difference between the elements

Question 14

Electronegativity

Answer 14

the power of an atom to attract the electron density in a covalent bond towards itself

Question 15

Electron pair repulsion

Answer 15

repulsion that exists between electron pairs due the negative electrons

Question 16

Electrostatic forces

Answer 16

strong forces of attraction between oppositely charged ions

Question 17

What is a hydrogen bond?

Answer 17

an interaction between a hydrogen atom and an electronegative atom

Question 18

Which elements does hydrogen bonding occur with?

Answer 18

nitrogen, fluorine, oxygen

Question 19

What happens in a hydrogen bond?

Answer 19

the slightly positive hydrogen is attracted to the lone pair on the electronegative atom

Question 20

Intermolecular forces

Answer 20

forces which exist between molecules

Question 21

What are the 3 types of intermolecular forces?

Answer 21

van der Waals, dipole-dipole, hydrogen bonds

Question 22

State the meaning of the term standard enthalpy of combustion.

Answer 22

Enthalpy change when one mole of a substance burns completely in
oxygen with all substances in their standard states

Question 23

Define the term enthalpy change.

Answer 23

heat change at constant pressure