2 - Atoms, ions and compounds

Question 1

mass within atoms

Answer 1

mass of proton = mass of neutron
electron gas negligible mass

Question 2

charges within atoms

Answer 2

electron is negative
proton is positive
neutrons has no charge

Question 3

atoms

Answer 3

protons = electrons
most neutrons = protons

Question 4

identity of an element

Answer 4

different elements have atoms with the different number of neutrons

Question 5

what does the atomic number show

Answer 5

number of neutrons in an atoms
-> as well as electron

Question 6

isotopes

Answer 6

atoms of the same element with different numbers of protons and therefore different atomic masses
- most elements are made of a mixture of isotopes

Question 7

isotopes and chemical reactions

Answer 7

• different isotopes of the same element have the same number of e-
• the number of neutrons have no effect on the reactions of that element
• so different isotopes of the same element react in the same way chemically

Question 8

ions

Answer 8

a charged atom, where the number of e- is different to neutron number

Question 9

what is the atomic mass unit u

Answer 9

the standard mass for atomic mass is 1 u, the mass of 1/12 th of the mass of a carbon atom
- approximately the mass of a proton or electron

Question 10

relative atomic mass

Answer 10

the weighted mean mass of an atom of an element relative to 1/12th of the mass of carbon-12

Question 11

relative atomic mass equation

Answer 11

sum (isotopes mass x relative abundance)/ total abundance

Question 12

copper ions

Answer 12

CU+
Cu2+

Question 13

Iron ions

Answer 13

Fe 2+
Fe 3+

Question 14

binary compounds

Answer 14

contains only two elements

Question 15

ammonium

Answer 15

NH4 +

Question 16

Hydroxide

Answer 16

OH-

Question 17

Nitrate

Answer 17

NO3 -

Question 18

Nitrite

Answer 18

NO2 -

Question 19

Hydrogencarbonate

Answer 19

HCO3 -

Question 20

Manganate (VII)

Answer 20

MnO4 -

Question 21

carbonate

Answer 21

CO3 2-

Question 22

sulfate

Answer 22

SO4 2-

Question 23

sulfite

Answer 23

SO3 2-

Question 24

dichromate (VI)

Answer 24

Cr2O7 2-

Question 25

phosphate

Answer 25

PO4 3-

Question 26

amount of substance -n

Answer 26

the number of particles in a substance

Question 27

how many particles does one mole of a substance contain

Answer 27

avogadro constant 6.02 x 10 ^23

Question 28

mass of one mole of any atom is

Answer 28

relative atomic mass

Question 29

equation linking mass mr and moles

Answer 29

n=mass/mr

Question 30

molecular formula

Answer 30

is the number of atoms of each element in a molecule

Question 31

empirical formula

Answer 31

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

Question 32

relative molecular mass

Answer 32

the weighted mean mass of a molecule of a compound compared with 1/12 th of the mass of an atom of carbon-12

Question 33

relative formula mass

Answer 33

the weighted mean mass of the formula unit of a compound compared with 1/12 th of the mass of an atom of carbon-12

Question 34

two assumptions when finding out the formula of a hydrated salts through experiment

Answer 34

1) all the water has been lost 2) no further decomposition

Question 35

1dm ^3 =

Answer 35

1000 cm3 = 1000ml = 1litre

Question 36

moles = of solution

Answer 36

c x V

Question 37

standard solution

Answer 37

a solution of a known concentration

Question 38

molar gas volume

Answer 38

volume per mole of gas molecules at stated temp and pressure

Question 39

what is RTP

Answer 39

20 'c and 101kPa

Question 40

at RTP 1 mole of gas has

Answer 40

volume 24 dm^3

Question 41

mole of a gas

Answer 41

volume / molar gas volume Vm must be of same units if V = dm3 than Vm is 24 if V is cm3 than Vm is 24000

Question 42

ideal gas equation and units

Answer 42

pV=nRT p= Pa (kPa -> Pa x10^3) V= m^3 (cm3 -> m3 x10^-6) or (dm3 -> m3 x10^-3) T= K ('C -> K +273)

Question 43

theoretical yield why is this not always possible

Answer 43

maximum possible amount of product - reaction may not have gone to completion - other reactions may have taken place (side reactions) - purification of the product may result in los of the product

Question 44

percentage yield

Answer 44

=actual yield / theoretical yield x 100

Question 45

limiting reagent

Answer 45

the reactant that is not in excess it is completely used up

Question 46

atom economy

Answer 46

- how well the atoms have been utilised = (sum of molar mass of desired products)/sum of molar mass of all products x 100

Question 47

reactions with high atom economies

Answer 47

- produce a large proportion of desired products and few unwanted waste products -make best use of natural resources

Question 48

why is atom economy not always the best way to see if a reaction is sustainable

Answer 48

- may use reactants that are sourced wrongly - other reactions can have a poor percentage yield but high atom economy