topic 4a: group 1 and 2

Question 1

trend in 1st IE down group 2

Answer 1

• atomic radius increases down the group
• more electron shells more shielding
• further distance nucleus from outer shell e-, weaker ESA
• less energy required to lose
• outweighs effect of increased no protons

Question 2

reactivity of group 2 metals down the group

Answer 2

• increases
• atomic radiu sincreases
• more shielding
• further distance nucleus and outer shell e-, weaker esa
• less energy required to lose
• outwewighs effect of increased no protons

Question 3

group 2 metal + O2

Answer 3

2Mg +O2 = 2MgO

Question 4

observation Mg with oxygen

Answer 4

bright white light

Question 5

consideration of using Mg in practicals etc?

Answer 5

• oxidises to form a thin layer of MgO
• must be cleaned off with an abrasive before

Question 6

group 2 metal + Cl2

Answer 6

Mg + Cl2 = MgCl2

Question 7

group 2 metal and STEAM !!!!!1

Answer 7

Mg + H2O = MgO + H2

Question 8

group 2 metal and WARM WATER

Answer 8

Mg + 2H2O = Mg(OH)2 + H2

Question 9

water after reaction with a group 2 metal

Answer 9

• alkaline
• hydroxide formed

Question 10

observations down the group of group 2 metals with water?

Answer 10

• more vigorous effervescence
• metal disappears
• exothermic (feels hotter)
• WHITE PPT FOR CALCIUM

Question 11

solubliity of group 2 hydroxides down the group

Answer 11

hydroxides are MORE soluble down th group
hence in the reactions w water, some are white ppt

Question 12

group 2 oxide + water

Answer 12

MgO + H2O = Mg(OH)2

Question 13

which is more basic, Mg(OH)2 or Ca(OH)2?

Answer 13

• calcium
• more soluble
• greater dissociation in water, so higher [OH-]

Question 14

group 2 hydroxiee / oxide + acid

Answer 14

• metal chloride
• water

Question 15

is magnesium ghydroxide soluble

Answer 15

no

Question 16

limewater reaction

Answer 16

Ca(OH)2 + CO2 = CaCO3 (SOLID) + H2O

Question 17

solubility of sulfates down group 2

Answer 17

less soluble
so baso4 the least soluble

Question 18

thermal decomposition

Answer 18

the use of heat to break down a reactant into 1+ product

Question 19

decomposition of a g2 carbonate

Answer 19

MgCO3 = MgO + CO2

Question 20

thermal stability of g2 carboantes down the group

Answer 20

• MORE thermally stable
• ionic radius of cation increases
• polarising power decreases
• co3 2- polarised less
• less strain (Weakening) on c-o bond
• so breaks less easily

Question 21

which of the g1 carbonates decompose and why?

Answer 21

ONLY LITHIUM
- tiny IR
- small enough to polarise the c-o bond in co3 2- so that the bond breaks and will decompose
-

Question 22

decomposition of lithium carbonate

Answer 22

Li2CO3 = Li2O + CO2

Question 23

decomposition of magnesium nitrate

Answer 23

2Mg(NO3)2 = 2MgO +4NO2 + O2

Question 24

observation of decomposition of group 2 nitrate

Answer 24

• brown gas NO2 evolving
• solid MELTS
• then white solid reforms

Question 25

trend in decomposition of g2 nitrates

Answer 25

- same as carbonates - mg2+ smallest IR, most polarising - puts most strain and weakens the n-o bond the most - most easy

Question 26

decomposition of group 1 nitrate

Answer 26

2NaNO3 = 2NaNO2 + O2 (nitrite + oxygen_

Question 27

which group 1 nitrate will decompose the same as a group 2 nitrate?

Answer 27

LITHIUM 4Li(NO3) = 2Li2O + 4NO2 + O2

Question 28

method of flame test

Answer 28

- nichrome/platinum wire [inert, high mp, no colour] - dip in conc HCl and then put in bunsen flame to clean - insert in sample - put in flame , and observe colour

Question 29

explain why there is colour

Answer 29

- heat energy - causes electron to excite move to higher energy level - then drops back down to ground state - energy is emitted as visible light

Question 30

if a gas is produced, water level

Answer 30

decreases

Question 31

describe exp for how to compare thermal stability of g2 NITRATES + a safety precaution

Answer 31

- fume cupbaord(NO2 TOXIC) - gas syringe, time taken to produce x volume of gas - use equal masses of nitrate, equal distance of bunsen so same strength of heating

Question 32

why do diff atoms show as diff colours

Answer 32

- energy levels are different distances apart - different aounts of energy emitted

Question 33

why if u mix 2 cations might u not be able to find out which 2 are present in a flame test?

Answer 33

darker colour obscures the lighter one

Question 34

why use HCl for step 2 of flame test?

Answer 34

forms volatile chlorides

Question 35

control variables for vailidity in the thermal stability of CARBOANTES test

Answer 35

- same MOLES of carbonate - same distance from BB - same volume LW

Question 36

phosphorus exists as

Answer 36

P4

Question 37

how to improve the exp about thermal stability of carbonates

Answer 37

- standardise by using disappearing cross