214 - Chemistry Questions Answers

IF VOLUME OF 1 MOLE OF STRNTIUM CHLORIDE (HAS FLUORITE STR) IS X CM3 & VOL OF UNIT CELL IS Y CM3 D NA CONSTANT IS GIVEN BY

ANS   ( X/Y) X4

Asked By: SARIKA SHARMA
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Joshi sir comment

since 1 unit cell of SrClcontains 4 molecules of the same so ratio will be 4X/Y

IN A FACE CENTRED CUBIC LATTICE A UNIT CELL IS SHARED EQUALLYBY HOW MANY UNIT CELLS

ANS 6

Asked By: SARIKA SHARMA
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Joshi sir comment

due to the reason that a unit cell contribute to 6 of the face attached memers

IN  CRYSTAL OF WHICH ONE OF D FOLLOWING IONIC COMPD. WOULD U EXPECT MAXm DISTANCE B/W CENTRE OF ANION &CATION

1)CsI

2)CsF

3)LiF

4)LiI

Asked By: SARIKA SHARMA
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Joshi sir comment

accordong to my opinion it will be CsI

C forms ccp, A is at 25%terahedral  viod &B is at 50% octahedral viod . if the particles along one of the fce diagonal are removed then formula?

ans A8B8C13

Asked By: SARIKA SHARMA
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Joshi sir comment

normal formula has C atom  =  1

                                     A atom = 2*1/4 = 1/2

                                     B atom = 1*1/2 = 1/2

so structure = C2AB = C4A2B2

now we have to remove atoms from one of the face diagonal so 

remove 2 corner C, so removed C = 1/8*2 = 1/4  and 1 face centre = 1/2                            sum = 3/4 

nothing else

so new formula = C4-3/4A2B2   = A8B8C13

 

if x is length of body diagonal ,then distance b/w 2 nearest cation in rock salt str is

ans    x/(61/2)

Asked By: SARIKA SHARMA
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Joshi sir comment

two nearest cations will be at corner and face centre so distance between these two will be  y   =    a/21/2

here a is side length and according to the given condition x = a31/2  

so a = x/ 31/2   

so  y = x  /  61/2

in the crystal str of Fe3O4 Fe2+& Fe3+ occupy resp.

50% octatrahedral  &12.5% tetrahedral viods

Asked By: SARIKA SHARMA
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Joshi sir comment

let atom of O = 1

so 50% Fe++ in octahedral void  = 1*1/2 = 1/2

and 12.5 % Fe+++ in tetrahedral voids = 2*1/8 = 1/4

so total Fe = 1/2 + 1/4 = 3/4

so name of the compound = Fe3/4O  = Fe3O4

d possible types of two dmensional lattice &3 D primitive unit cells are resp.

ans 5& 7

Asked By: SARIKA SHARMA
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Joshi sir comment

and in 3 D these are 7 crystal system, I have given an article for these 7 already

how many atoms are there in a cubic unitcell having one atom on each corner &two atoms on each body diagonal of cube?

& also if instead 2 there are 3 atoms at body diagonal?

Asked By: SARIKA SHARMA
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Joshi sir comment

corner atoms = 8*1/8 = 1

diagonal atoms = 4*2 = 8

total = 9

in second case calculate similarly

Emf of the cell Ni/Ni+2||Au+3/Au at 298 K will b?    [EoNi/Ni+2 = 0.25 V,EoAu/Au+3= -1.5V]

Asked By: AYANSH
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Joshi sir comment

 

Ecell = E0cell - (0.0591/n)  log {[Ni++]3 / [Au+++]2}

Reactions are 3Ni ------> 3Ni++   +   6e-

and      2Au+++ +   6e- ---------->   2Au  

now put E0cell = E0c - E0= 1.5 - (-0.25)      here you should remember that you have to take only reduction potentials not oxidation potentials

                                               = 1.75

n = 6  and concentrations if given otherwise take these two equal to zero.

IS BASICITY OF ACETIC ACID IS 1? PLS SEND THE BASICITY OF OTHER ACIDS WHICH ARE USUALLY ASKED  IN ENTRANCE EXAM

Asked By: SARIKA SHARMA
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Joshi sir comment

HCl, HNO3 , HCOOH are mono basic acids

COOH-COOH, H2SO4 are di basic acids

similarly others 

 

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