Group 1+2 Flashcards
Equation for decomposition of group 1 carbonates (except Li)
Oxide and CO2 produced
XCO3➡️ XO+CO2
E.g KCO3➡️ KO+CO2
Equation for decomposition of Li carbonate (exception for group 1)
LiCO3➡️ LiO2+CO2
Equation for decomposition of group 1 nitrates (except Li)
Form nitrite and oxygen
E.g. 2KNO3➡️ 2KNO2+O2
How thermally stable are carbonates in group 1?
Very, decompose at high temps (won’t decompose under Bunsen)
E.g. When heating BaCO3 it gets so hot the test tube melts
Why does thermal stability increase down groups 1 and 2?
Larger cations
Lower charge density (charge spread over larger area)
Less distortion (caused by positive ion)
More at stable
What happens to the solubility of group 1+2 hydroxides down the group?
Solubility increases
What happens to the solubility of group 1+2 sulphates as you go down the group?
Solubility decreases
Why are group 2 compounds less thermally stable than group 1 compounds?
Greater charge on cation
Greater distortion
Less stable
Equation for decomposition of group 2 carbonates
Oxide and CO2 produced
XCO3➡️ XO+CO2
E.g MgCO3➡️ MgO+CO2
Equation for decomposition of group 2 nitrates
Oxide, nitrogen dioxide and oxygen produced
E.g 2Mg(NO3)2 ➡️ 2MgO+4NO2+O2
What do you measure when testing for nitrate decomposition? (O2)
How long it takes for a certain amount of O2 to be produced
E.g. Enough to relight glowing splint
What do you measure when testing for nitrate decomposition? (NO2)
How long it take for a certain amount of NO2- brown gas- is produced.
Toxic- done in fume cupboard
What do you measure when testing for carbonate decomposition?
Time it takes for certain amount of CO2 to be produced.
E.g. Bubble through limewater, turns cloudy
Flame colour of Li?
Red
Flame colour of Na?
Orange/yellow
Flame colour of k?
Lilac
Flame colour of Rb?
Red
Flame colour of Cs?
Blue
Flame colour of Ca?
Brick red
Flame colour of Sr?
Crimson
Flame colour of Ba?
Green
Equation for decomposition of Li nitrate
Produced oxide, nitrogen oxide and oxygen
4LiNO3➡️ 2Li2O+4NO2+O2
How are flame colours produced?
Electrons excited by thermal energy (jump to higher energy levels)
Colour produced from energy emitted as they return (lower levels)
How is a flame test done?
Mix small amount of compound with HCl
Heat platinum/nichrome wire in hot flame (Bunsen)
Dip wire into compound and put in flame
Equations for group2+water reactions
Forms metal hydroxide and hydrogen
E.g. Mg+2H2O ➡️ Mg(OH)2+H2
What happens to reactivity of (gr2+water) reaction down the group?
Reactivity increases
E.g. Mg- slow, little observations
Ba- fast, lots of bubbles
Equations for gr2+oxygen reaction
Forms solid, white oxides
E.g. 2Mg+O2➡️ 2MgO
Equations for gr2+chlorine reactions
Forms solid, white chlorides
E.g. Mg+Cl2➡️ MgCl2
Gr2 oxides reaction with water- equation
MO(s)+H2O➡️M(OH)2 (aq)
Gr2 oxides reaction with dilute acid- equation
MO(s)+HCl➡️MCl2(aq)+H2O
Gr2 hydroxides reaction with water: equation
M(OH)2(s) +H2O➡️ M(OH)2(aq)
Gr2 hydroxides reaction with dilute acid:equation
M(OH)2(aq) + 2HCl➡️ MCl2(aq) + 2H2O
