atoms and molecules.docx

7/23/2019 Atoms and Molecules.docx

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Chapter-3

Atoms and Molecules

SOLUTION OF NCERT IN TEXT QUESTIONS:-

QUESTIONS ON (PAGE NO.-31,32):-

Q!:- In a "eact#on$ %& ' o( sod#um ca")onate "eacted *#t+ , ' o( et+ano#c ac#d

T+e "oducts *e"e .. ' o( ca")on d#o/#de$ 01 ' *ate" and 2. ' o( sod#um

et+anoate S+o* t+at t+ese o)se"3at#ons a"e #n a'"eement *#t+ t+e la* o(

conse"3at#on o( mass

Sod#um ca")onate 4 et+ano#c ac#d 5 sod#um et+anoate 4 ca")on d#o/#de 4

*ate"

Ans:- In t+e '#3en "eact#on$ sod#um ca")onate "eacts *#t+ et+ano#c ac#d to

"oduce sod#um et+anoate$ ca")on d#o/#de$ and *ate"

Total mass o( "eactants 6 Mass o( 7Sod#um ca")onate 4 Et+ano#c ac#d8

6 %&' 4 ,0'$ 6 !!&'

Total mass o( "oducts 6 Mass o( 7Sod#um et+anoate 4 Ca")on d#o/#de 4 9ate"8

6 ..' 4 2.' 4 01'$ 6 !!&'

S#nce$ t+e total mass o( "eactants #s eual to t+at o( t+e total mass o("oducts$ +ence t+ese o)se"3at#ons a"e t+e la* o( conse"3at#on o( mass

Q.:- ;


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Q?:- 9+#c+ ostulate o( @altons atom#c t+eo"< can e/la#n t+e la* o(

deBn#te "oo"t#ons=

Ans:- T+e ostulate o( @altons atom#c t+eo"< *+#c+ can e/la#n t+e la* o(

deBn#te "oo"t#on #s:-

The re&at!$e "+m%er a"# !"# o atom !" a !$e" 'ompo+"# rema!" 'o"ta"t*

QUESTIONS ON (PAGE NO.-3/):-

Q!:- @eBne atom#c mass un#t

Ans:- Atom#c mass un#t:- Mass un#t eual to e/actl< one-t*el(t+ t+e mass o( o"e

atom o 'ar%o"-12#s called one atom#c mass un#t It #s *"#tten as u

! amu 6 !,,

1027

D' 7,0..

1023

8

Q.:- 9+< #s #t not oss#)le to see an atom *#t+ naDed e


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Atom#c num)e":- !& !H Al

Cl

Elect"on#c conB'u"at#on:- .$2$& .$2$H &

!

alenc


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Q&:- 9+at #s meant )< t+e te"m c+em#cal (o"mula=

Ans:- T+e c+em#cal (o"mula o( a comound means:-

The m%o&!' repree"tat!o" o the 'ompo!t!o" o a 'ompo+"#.*

F"om t+e c+em#cal (o"mula o( a comound$ *e can Dno* t+e num)e" and

D#nds o( atoms o( d#e"ent elements t+at const#tute t+e comound

Fo" e/amle:- F"om t+e c+em#cal (o"mula COG o( 'ar%o" #!o0!#e$ *e come to

Dno* t+at o"e 'ar%o" atom and to o0e" atom a"e c+em#call< )onded

to'et+e" to (o"m one molecule o( t+e comound$ 'ar%o" #!o0!#e

Q?:- ;o* man< atoms a"e "esent #n a:-

! ;GS molecule and

. 3

O4

#on=

Ans:- 7#8 In an ;GS molecule$ three atoma"e "esent t*o o( h#roe"and one

o( +&ph+r

7##8 In a 3

O4

#on$ $e atom a"e "esent one o( phophor+ and (ou" o(

o0e"

QUESTIONS ON (PAGE NO.-4):-

Q!:- Calculate t+e molecula" masses o( ; G$ OG$ ClG$ COG$ C;K$ CG;P$ CG;K$ N;$

C;O;

Ans:- 7!8 Atom#c mass o( ;


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ClG conta#ns . atoms o( C+lo"#ne

So$ Molecula" mass o( C+lo"#ne 7ClG8 6 &%% . 6 H!u

7?8 Atom#c mass o( Ca")on 7C8 6 !.u

Atom#c mass o( O/


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So$ Molecula" mass o( N;$ 6 !? ! 4 ! & 6 !? 4 . 6 !Hu

718 Atom#c mass o( Ca")on 7C8 6 !.u

Atom#c mass o( ;


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Mola" mass o( sod#um 7Na8 6 .&'

! mole 6 ,0.. 1023

atoms

Num)e" o( atoms #n .&' o( sod#um 7Na8 6 ,0..

10

23

atoms

Num)e" o( atoms #n !' o( sod#um 7Na8 66.02210

23

23

Num)e" o( atoms #n !00' o( sod#um 7Na8 66.022 10

23

23 !00

6 .,!2 1023

Mola" mass o( #"on 7Fe8 6 %,'

! mole 6 ,0.. 1023

atoms

Num)e" o( atoms #n %,' o( #"on 7Fe8 6 ,0.. 1023

atoms

Num)e" o( atoms #n !' o( #"on 7Fe8 66.02210

23

56

Num)e" o( atoms #n !00' o( #"on 7Fe8 66.02210

23

56 !00

6 !0H% 1023

T+us$ t+e"e *#ll )e mo"e atoms #n !00' o( Sod#um as comound to !00' o(

#"on

SO5UTION O6 NCE7T E8E7CISE :-

Q!:- A 0.?' samle o( comound o( o/


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o( )o"on 6Mass of the boron

Mass of the compound !00

o( )o"on 60.096g

0.24g

!00

o( )o"on 6 ?0

o( O/


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S


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alenc


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Ans:-

A Mola" mass o( Et+


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Atom#c mass o( O/


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C ..' o( ca")on d#o/#de

Ans:- No o( moles 7n8 6Givenmass(m)

Molar mass(M)

A !.' o( o/


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W ! mole o( *ate" molecules 7;GO8 6 Y! . 4 !, !Z 6 !2'

% mole o( *ate" molecules 6 0% !2' 6 10'

Q!0:- Calculate t+e num)e" o( molecules o( sul+u" 7S 8 "esent #n !,' o(sol#d sul+u"

Ans:-Solut#on:- Molecula" mass o( sul+u" 7S8 6 &. 2 6 .%,'

! mole 6 ,0.. 1023

molecule

T+e"e(o"e$ t+e num)e" o( molecules #n .%,' 7!mole8 sul+u" 6 ,0..

1023

T+e num)e" o( molecules #n !' sul+u" 66.02210

23

256

T+e num)e" o( molecules #n !,' sul+u" 66.02210

23

256 !,

6 &H, 1023

T+e"e(o"e$ #n !,' o( sol#d sul+u" t+e"e *#ll )e &H, 1023

molecules

Q!!:- Calculate t+e num)e" o( alum#n#um #ons "esent #n 00%!' o( alum#n#um

o/#de

Y;#nt:- t+e mass o( an #on #s t+e same as t+at o( an atoms o( t+e same element

Atom#c mass o( Al 6 .HuZ

Ans:- Solut#on:- Mass o( ! mole alum#n#um o/#de 7AlGO8 6 Y.H . 4 !,

&Z 6 !0.'

!0.' 6 ! mole

00%!' 61

102 00%!$ 6 %

104

mole

!?


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Num)e" o( #ons o( alum#n#um #n ! mole alum#n#um o/#de 7AlGO8 6 .

,0.. 1023

Num)e" o( #ons o( alum#n#um #n % 104

mole alum#n#um o/#de 7AlGO8

6

6 . ,0.. 1023

% 104

6

,0.. 1020

EXAMINATION BASED OTHER IMPORTANT QUESTIONS

Short 9 5o" a"er tpe +et!o" :-

Q!:- 9+at


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In t+#s "eact#on 'a&'!+m o0!#e and ater a"e "eactants *+#le 'a&'!+m

h#ro0!#e#s "oduct

Q.:- E/la#n La*s o( C+em#cal Com)#nat#ons *#t+ an e/amle

Ans:-La*s o( C+em#cal Com)#nat#ons :- T+e"e a"e t*o la*s o( c+em#cal

com)#nat#on

! La* o( Conse"3at#on o( Mass

. La* o( Constant "oo"t#ons

& La* o( Mult#le "oo"t#ons

! La* o( Conse"3at#on o( Mass :- A"to!"e 5. 5a$o!!er*$ a F"enc+ sc#ent#st$

esta)l#s+ed t+e t+eo"< o( La* o( Conse"3at#on o( Mass T+e la* o(

conse"3at#on o( mass states$

;a 'a" "e!ther %e 'reate# "or #etroe# !" a 'hem!'a& rea't!o"*.

Acco"d#n' to t+#s la* total mass o( "oducts #s a&a e+a&to t+e total

mass o( rea'ta"t

E/amle:- 9+en 'a&'!+m o0!#e #s d#ssol3ed #n ater, 'a&'!+m h#ro0!#e #s

(o"med T+e "eact#on #n3ol3e #n t+#s can )e *"#tten as:-

In t+#s "eact#on 'a&'!+m o0!#e and ater a"e "eactants *+#le 'a&'!+m

h#ro0!#e#s "oduct

In t+#s "eact#on H? ' o( calc#um +


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. La* o( Constant "oo"t#ons:- La* o( Constant "oo"t#on states t+at:-

A 'hem!'a& 'ompo+"# a&a 'o"ta!" e0a't& the ame proport!o" o e&eme"t

% ma*.

T+#s la* #s also Dno*n as 5a o #e"!te proport!o"*


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In ca")on d#o/#de 7CO G 8:- !.' o( ca")on com)#ne *#t+ &.' o/


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, @alton atom#c t+eo"< stated t+at atoms o( d#e"ent com)#ne #n s#mle

"at#o T+#s #s 3al#d (o" ma^o"#t< o( t+e s#mle and small molecules Wut #n

case o( la"'e" o" )#''e" and comle/ molecules t+e #dea o( s#mle "at#o

does not +old

E/amle:- Su'a":- C_G;GGO__ and "at#o #s:- !. : .. : !!

Q%:- E/la#n mod#Bed @alton atom#c t+eo"


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H T+e s#e o( atoms #s #nd#cated )< #ts "ad#us

2 In anc#ent t#me atoms *as cons#de"ed #nd#3#s#)le

S


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S


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T+us atom#c mass #s t+e "elat#3e atom#c mass o( an atom *#t+ "esect to

![!.t+ o( t+e mass o( ca")on-!. atom amu #s t+e a))"e3#at#on o(

Atom#c mass un#t$ )ut no* #t #s denoted ^ust )< u

T+e atom#c mass o( +


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E/amle:-!:- F#nd t+e a)solute mass o/


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E/#stence o( Atoms:-Atoms o( most o( t+e elements e/#st #n t+e (o"m o( mo&e'+&e

o" !o"$ s#nce t+e< a"e mot rea't!$e

Fo" e/amle:- ;


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E/amle:-

;


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? Tet"a-atom#c:- 9+en molecule #s (o"med )< t+e com)#nat#on o( (ou" atoms

#t #s called tet"a-atom#c molecule

Fo" e/amle:- +os+o"ous molecule 7K8

% ol


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Q!.:- 9+at


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On t+e )ases o( atoms:-

! Monoatom#c #ons:- Ions (o"med )< one atom a"e called monoatom#c #ons

. ol


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