Chemical Properties

Question 1

Reaction with Air
i)Li + air
ii)Na+ air
iii)K+ air
iv)Be,Mg + air at RT
v)Ca + air
vi)Li3N + H2O
vii)CaO + H2O
viii)Na2O2 + H2O
ix)KO2 + H2O

Answer 1

i)Li + air —->Li3N + Li2O
ii)Na+ air—->Na2O2
iii)K + air —->KO2
iv)Be,Mg + air—->no rxn
v)Ca + air—->Ca3N2 + CaO
vi)Li3N + H2O—->LiOH + NH3
vii)CaO + H2O—–>Ca(OH)2
viii)Na2O2 + H2O —->NaOH + H2O2
ix)KO2 + H2O —->KOH + H2O2 + O2
here O2- disproportionates into O2-2 and O2

Question 2

chemical rxns when KO2 is heated and is exposed to CO2

Answer 2

KO2—>K2O + O2
K2O + CO2 —>K2CO3

Question 3

Reactivity towards water:
1)Alkali Metals
Kinetics:(rate of rxn)
Thermodynamics:(net energy release)
2)Alkaline Earth Metals
Kinetics:(rate of rxn)
Thermodynamics:(net energy release)

Answer 3

1)Alkali Metals
Kinetics:
Li<Na<K<Rb<Cs(inversely proportional to IE)
Thermodynamics:
Na<K<Rb<Cs<Li(Li has high HE)
Kinetics and Thermodynamics:
Be<Mg<Ca<Sr<Ba

Question 4

Reaction with ammonia gas,H2C2,alcohol:
for alkali metals:
Na+C2H5OH
M (M!=Li)+ NH3(g)
Li + NH3(g)
M(M!-Li) + H2C2(g)
Li + H2C2

Answer 4

Na + C2H5OH—>C2H5O-Na+ +H2
M + NH3(g)—>MNH2 + H2
Li + NH3(g)—>Li2NH + H2
M + H2C2—->M2C2 + H2
Li + H2C2 —->no rxn

Question 5

rxn of dil solution of Alkali Metal in liq.NH3:
rxn on standing:

Answer 5

rxn of dil solution of Metal in liq.NH3:
M(s) + NH3(l) —->M+(amm.) + e-(amm.)(blue in color)
rxn on standing:
M + liq.NH3 —>MNH2 + H2

Question 6

color of solution of alkali metal in liq.NH3 when
i)on increasing conc., paramagnetism increases and conductivity increases
ii)on increasing conc.,paramagnetism decreases and conductivity decreases

Answer 6

i)blue
ii)bronze

Question 7

compare enthalpy of formation
i)LiF,NaF,KF,RbF,CsF
ii)LiCl,NaCl,KCl,RbCl,CsCl

Answer 7

i)LiF>NaF>KF>RbF>CsF
ii)LiCl<NaCl<KCl<RbCl<CsCl

Question 8

MOP of
i)BeF2
ii)BeCl2

Answer 8

i)(NH4)2BeF4–heat–>NH3+HF+BeF2
ii)BeO+Cl2+C—>BeCl2 +CO

Question 9

i)BeF2(s) structure
ii)BeCl2,BeBr2,BeI2 solid state structure and gaseous state structure

Answer 9

i)like SiO2
ii)solid state chain polymer and gaseous state dimer

Question 10

MP of alkali metal halides
i)MF,MCl,MBr,MI
ii)LiCl,NaCl,KCl,RbCl,CsCl
iii)LiF,NaF,KF,RbF,CsF

Answer 10

i)MF>MCl>MBr>MI(proportional to ionic character and Lattice Energy)
ii)NaCl>KCl>RbCl>CsCl>LiCl(LiCl is predominantly covalent)
iii)NaF>KF>LiF>RbF>CsF

Question 11

LiAlH4 + BeCl2

Answer 11

LiAlH4 + BeCl2–>BeH2 + LiCl + AlCl3

Question 12

structure of BeH2
i)in gaseous state
ii)in solid state

Answer 12

i)gaseous state Be2H4
ii)solid state chain polymer