mod 2 foundations

Question 1

isotopes

Answer 1

same number of protons & electrons different number of neutrons

Question 2

Relative atomic mass

Answer 2

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

Question 3

Relative isotopic mass

Answer 3

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

Question 4

Calculate RAM

Answer 4

(% x mass) + (% x mass)

100

Question 5

Moles

Answer 5

The amount of substance that contains 6.02 x 10^23 of particles same as 12g of carbon-12

Question 6

avogadros constant

Answer 6

6.022 x 10^23

N= n x NA

Question 7

Ideal gas law

Answer 7

PV = nRT
P=pressure (pa)
V=volume(m3)
R=constant(8.31)
T=temp (k)

Question 8

properties of ideal gas law

Answer 8

• all particles are identical & in random continuous motion
• particles travel in straight lines
• the particles dont react when they collide
• the particles have no intermolecular forces between them

Question 9

Molar gas volume

Answer 9

At room temp and pressure, 1 mole of gas occupies a volume of 24dm3
V= n x 24dm3

Question 10

Percentage yield

Answer 10

actual yield / theoretical yield

x100

Question 11

Atom economy

Answer 11

Mr of desired product / sum of all Mr of reactants

Question 12

Water of crystalisation

Answer 12

Water molecules that form part of the crystalline structure
anhydrous-dehydrated (no water)
hydrated(water)

Question 13

metallic bonding

Answer 13

strong electrostatic force of attraction between positively charged ions and sea of delocalised electrons

• high melting and boiling points
• good conductors (solid&liquid)
• malleable&ductile

Question 14

covalent bonding

Answer 14

strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atom
eg-N2,CO2

Question 15

Dative covalent bond

Answer 15

one element gives both electrons to the bond

eg-NH4

Question 16

Ionic bonding

Answer 16

electrostatic attraction between positive & negative ions
-metal&non metal
-giant lattices
higher the charge the stronger the bond

Question 17

general equations

Answer 17

Acid + metal = salt + hydrogen
Acid + base =salt +water
Acid + metal carbonate= salt+ water+ carbon dioxide

Question 18

Oxidation state

Answer 18

tells us the charge of an element, indication of how many electrons an element has lost or gained

Question 19

oxidation state rules

Answer 19

-all elements in their uncombined state has an oxidation state of 0
-oxygen normally -2
cl is different if binded with fluorine or oxygen
-hydrogen have +1 unless bonded to metal -1

Question 20

bases

Answer 20

substances that can react with an acid to forma salt

• sodium hydroxide (NaOH)
• potassium hydroxide(KOH)
• ammonia- (NH3)

Question 21

electron shells

Answer 21

2,8,18,32
s=2, p=6, d=10 f=14
1s,2s,2p,3s,3p,4s,3d etc

Question 22

orbitals

Answer 22

s-orbitals 
sphere shape
p orbitals
-dumbell shape (3 kinds)
each orbital hold 2 electrons so therefore in p shell there are 3 orbital shells

Question 23

short hand notation

Answer 23

write the nearest noble gas in square brackets then write the continuing shells

Question 24

electron configuration

Answer 24

-draw with single headed arrows
opposite way to eachother as electrons repel
-put electrons in each box before filling each pair out
most stable if half full or full

Question 25

shapes of molecules

Answer 25

``` linear = 180 (co2) triganal planar = 120 (BCl3) tetrahedral = 109.5 (CH4) pyramidal = 107 (NH3) non-linear = 104.5 (H2O) octahedral = 90 (SF6) -lone pairs repel more than bonded ```

Question 26

electronegativity

Answer 26

-an atoms ability to attract bonding electrons in a bond -measured using pauling scale -Across periodic table; electronegativity increases,nuclear charge increases, ar decreases less than 0.5 = non polar 0.5 - 1.8 = polar bigger than 1.8 = ionic

Question 27

Bond polarity

Answer 27

non polar- if elements are similar in electronegativity or the same eg H2 polar- if electronegativities are different eg HCl separation of opposite charges (dipoles) Solvents dissolve in like substances polar dissolves in polar

Question 28

intermolecular forces

Answer 28

``` induced dipole (london forces) - weak forces that exist between all molecules; electrons move to one side causing a temporary charge permanent dipole - stronger than london; exist in polar covalent bonds hydrogen - strongest force; dipole bonds with lone pair, between H-N,F,O ```

Question 29

Anomolous water properties

Answer 29

ice is less dense than water - hydrogen bonds hold water molecules apart in a lattice - water has relatively high boiling point - high surface tension

Question 30

empirical formula

Answer 30

simplist whole number ratio -work out number of moles of each then divide by smallest number of moles will give you a ratio then round to nearest whole number

Question 31

uncertainty

Answer 31

% = (2x) uncertainty / quantity measured x100 -(2x) if using a burette as there are 2 uncertainties

Question 32

compound charges

Answer 32

``` sulphate - SO4 (2-) nitrate - NO3 (-) carbonate CO3 (2-) hydroxide OH (-) ammonium NH4 (+) ```