physical...dbts

Q1 The closest distance b/w 2 atoms among these unit cells (assuming edge length =a in eache cell)
a)diamond
b)FCC

Q2 When NH4Cl is dissolved in H2O ,the temp of H2O decreases hten
a)ΔHs>0,ΔHi<ΔHh
b)ΔHs<0,ΔHi<ΔHh
c)ΔHs<0,ΔHi>ΔHh
d)ΔHs>0,ΔHi>ΔHh

where ΔHs=enthalpy of soln,ΔHi=enthalpy of ionisation,ΔHh=enthalpy of hydration of ions

Q3 Ammonium nitrate product favouredly dissolves in water at room temp and process causes teh soln to become quite cold.Whic hof the following is true abt dissolution fo ammonium nitrate
a)process is exothermic
b)solublity is greater in warmer water
c)ΔS° <0
d)All solns of ammonium nitrate are supersaturated

6 Answers

106
Asish Mahapatra ·

Q2. (a)
Q3. (b) ??

24
eureka123 ·

2) is wrong..but 3 is right......tell me reason plz

106
Asish Mahapatra ·

Q3. Le chatelier's principle..
endothermic reactions.. temp increases reaction proceeds forward

Q2. I always get confused... when we compare delta H , do we compare their magnitudes only or their signs included???

If magnitude only then (d)

24
eureka123 ·

i think magnitude only...

and thx for 3.....but can u tell me how is optiond d) related to Q3 ???

106
Asish Mahapatra ·

no idea...

29
govind ·

diamond forms a lattice similar to Zinc blende structure..
so closest distance b/w two atoms will be the distance ot the tetrahedral void from the corner = √3/4 a

and in fcc the closest distance is b/w the atom placed at the corner and on the same face...= √2/4 a

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