Ch9 Group 2 qualitative analysis Flashcards
G2 Chemical properties
Have two electrons in outer shell so form 2+ cations
reducing agents
G2 Physical properties
Metals
- good conductors of electricity
-form colourless ionic compounds
-high mpt + bpt
Trend in G2 reactivity
Increases down a group as loses electron more easily
- atomic radius increases
- shielding effect increases
- nuclear charge increasing has no effect
- first ionisation energy decreases
G2 reaction with oxygen general equation (flame test)
M(s) + 1/2 O2 -> MO(s)
Mg flame test
white
Ca flame test
brick-red
Sr flame test
crimson
Ba flame test
green
G2 reaction with water basic equation
M(s) + 2H2O(l) -> M(OH2) (aq) + H2(g)
rate of reaction increases down group
Mg reaction with water
reacts very slowly with water to produce Mg(OH)2 solid - white ppt
reacts more readily with steam to form MgO(s)
G2 reaction with chlorine
forms white chlorides
M(s) + Cl2(g) -> MCl2(s)
G2 reaction with dilute acids
produces salt and hydrogen gas
M(s) + 2HCl(g) -> MCl2(aq) + H2(g)
Reaction of G2 oxide with water
MO(s) + H2O(l) -> M(OH)2 (aq)
magnesium hydroxide
sparingly soluble
forms white suspension- used to treat indigestion
reaction of G2 oxide with acid
MO(s) + 2HCl(aq) -> MCl2(aq) + H2O(aq)
