Atoms and Reactions

Question 1

what is empirical formula

Answer 1

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

Question 2

what is molecular formula

Answer 2

number and type of atoms of each element in a molecule

Question 3

what is structural formula

Answer 3

shows how atoms in a molecule are bonded together

Question 4

what is displayed formula

Answer 4

molecule drawn out by showing all bonds

Question 5

what does hydrated mean

Answer 5

contains water molecules (water of crystallisation) as part of the crystalline structure

Question 6

what does anhydrous mean

Answer 6

contains no water of crystallisation

Question 7

what is water of crystallisation

Answer 7

the water molecules contained within a crystalline structure

Question 8

1 mol of particles…

Answer 8

contains the same number of particles as there are atoms in exactly 12g of carbon-12

Question 9

the avogadro constant

Answer 9

the number of particles in 1 mol of a substance - 6.02x10^23

Question 10

what is a mol

Answer 10

the amount of substance that contains the same number or particles as there are exactly in 12g of carbon 12

Question 11

what is molar mass

Answer 11

the mass of one mol of a substance. gmol-1

Question 12

what is molar gas volume

Answer 12

1 mol of any gas occupies the same volume at given temp and pressure - 24dm3 rtp, 22.4dm3 stp

Question 13

what is atomic number

Answer 13

number of protons in an atom (also number of electrons)

Question 14

what is mass number

Answer 14

number of protons + neutrons

Question 15

what is an isotope

Answer 15

atom of the same element with the same number of protons but different number of neutrons and so different masses

Question 16

what is relative isotopic mass

Answer 16

mass of an isotope compared with 1/12 of the mass of an atom of carbon-12

Question 17

what is relative atomic mass Ar

Answer 17

weighted mean mass of an atom of an element compared with 1/12 of the mass of carbon-12

Question 18

what is relative molecular mass mr

Answer 18

mass of a molecule compared with 1/12 of the mass of atom carbon-12

Question 19

what is relative formula mass

Answer 19

mass of a formula unit compared with 1/12 of the mass of atom carbon-12

Question 20

what is a mass spectrometer used for

Answer 20

to find the percentage of abundance of the isotopes present in a sample of an element

Question 21

what is vaporisation

Answer 21

the sample to be tested is turned to a gas

Question 22

reasons for not 100% yield

Answer 22

• material lost during the reaction (when filtering distilling transferring)
• reaction not going to completion
• completing side reaction occurring alongside main reaction

Question 23

why do scientists convert as much of the raw materials into useful products

Answer 23

• to increase profits
• to preserve natural resources
• to reduce waste and pollution

Question 24

what happens with increased pressure

Answer 24

lower volume as same number of particles pushed closer together

Question 25

what does increased temperature do

Answer 25

higher volume (same number of particles have more energy so moving faster - to keep pressure the same, volume must be greater so same number of collisions with walls of container)

Question 26

what is an acid

Answer 26

a proton donor and release H+ ions into solution

Question 27

what is a base

Answer 27

a proton acceptor

Question 28

what is an alkali

Answer 28

a soluble base

Question 29

what is a salt

Answer 29

a substance formed when H+ ions in an acid are replaced by metal ions or ammonium ions

Question 30

what do acids do

Answer 30

release H+ ions into aqueous solution

Question 31

what does a weak acid do

Answer 31

it only partially dissociates in solution

Question 32

what does a strong acid do

Answer 32

fully dissociates in solution

Question 33

what do bases do

Answer 33

neutralises an acid by reacting with H+ ions

Question 34

what do alkalis do

Answer 34

produce OH- ions in solution

Question 35

when do salt reactions happen

Answer 35

during a neutralisation reaction

Question 36

what is oxidation

Answer 36

loss of e- and an increase in ox number

Question 37

what is reduction

Answer 37

gain of electron and decrease in ox number

Question 38

what is an oxidising agent

Answer 38

an element compound that causes oxidation of another (accepts e- so are reduced)

Question 39

what is a reducing agent

Answer 39

an element or compound that causes reduction of another (lose e- so are oxidised)

Question 40

what are covalent bonds

Answer 40

the electrostatic attraction between the positive nuclei and a shared pair of electrons

Question 41

what is electronegativity

Answer 41

the ability of atom to attract a bonding pair of electrons in a bind (covalent) to itself

Question 42

what causes greater electronegativity

Answer 42

the higher the nuclear charge and closer the bonding electrons are to the nucleus