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Grade 11 Exam  >  Grade 11 Notes  >  Chemistry for Grade 11  >  Past Year Paper with solution: Chemistry, 2018, Class 11

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 Page 1


C B S E 	 C l a s s 	 – 	 X I
C H E M I S T R Y
T i m e 	 a l l o w e d : 	 3 	 h o u r s , 	 M a x i m u m 	 M a r k s : 	 7 0
G e n e r a l 	 I n s t r u c t i o n s :
a ) 	 A l l 	 t h e 	 q u e s t i o n s 	 a r e 	 c o m p u l s o r y .
b ) 	 T h e r e 	 a r e 	 2 6 	 q u e s t i o n s 	 i n 	 t o t a l .
c ) 	 Q u e s t i o n s 	 1 	 t o 	 5 	 a r e 	 v e r y 	 s h o r t 	 a n s w e r 	 t y p e 	 q u e s t i o n s 	 a n d 	 c a r r y 	 o n e 	 m a r k 	 e a c h .
d ) 	 Q u e s t i o n s 	 6 	 t o 	 1 0 	 c a r r y 	 t w o 	 m a r k s 	 e a c h .
e ) 	 Q u e s t i o n s 	 1 1 	 t o 	 2 2 	 c a r r y 	 t h r e e 	 m a r k s 	 e a c h .
f ) 	 Q u e s t i o n s 	 2 3 	 i s 	 v a l u e 	 b a s e d 	 q u e s t i o n 	 c a r r y i n g 	 f o u r 	 m a r k s .
g ) 	 Q u e s t i o n s 	 2 4 	 t o 	 2 6 	 c a r r y 	 f i v e 	 m a r k s 	 e a c h .
h ) 	 T h e r e 	 i s 	 n o 	 o v e r a l l 	 c h o i c e . 	 H o w e v e r , 	 a n 	 i n t e r n a l 	 c h o i c e 	 h a s 	 b e e n 	 p r o v i d e d 	 i n 	 o n e 	 q u e s t i o n
o f 	 t w o 	 m a r k s , 	 o n e 	 q u e s t i o n 	 o f 	 t h r e e 	 m a r k s 	 a n d 	 a l l 	 t h r e e 	 q u e s t i o n s 	 i n 	 f i v e 	 m a r k s 	 e a c h . 	 Y o u
h a v e 	 t o 	 a t t e m p t 	 o n l y 	 o n e 	 o f 	 t h e 	 c h o i c e s 	 i n 	 s u c h 	 q u e s t i o n s .
i ) 	 U s e 	 o f 	 c a l c u l a t o r s 	 i s 	 n o t 	 p e r m i t t e d . 	 H o w e v e r , 	 y o u 	 m a y 	 u s e 	 l o g 	 t a b l e s 	 i f 	 n e c e s s a r y .
1 . 	 D r a w 	 t h e 	 s t r u c t u r e 	 o f
a ) 	 2 , 3 - D i m e t h y l p e n t a n e
b ) 	 4 - P h e n y l b u t - 1 - e n e
A n s .
Page 2


C B S E 	 C l a s s 	 – 	 X I
C H E M I S T R Y
T i m e 	 a l l o w e d : 	 3 	 h o u r s , 	 M a x i m u m 	 M a r k s : 	 7 0
G e n e r a l 	 I n s t r u c t i o n s :
a ) 	 A l l 	 t h e 	 q u e s t i o n s 	 a r e 	 c o m p u l s o r y .
b ) 	 T h e r e 	 a r e 	 2 6 	 q u e s t i o n s 	 i n 	 t o t a l .
c ) 	 Q u e s t i o n s 	 1 	 t o 	 5 	 a r e 	 v e r y 	 s h o r t 	 a n s w e r 	 t y p e 	 q u e s t i o n s 	 a n d 	 c a r r y 	 o n e 	 m a r k 	 e a c h .
d ) 	 Q u e s t i o n s 	 6 	 t o 	 1 0 	 c a r r y 	 t w o 	 m a r k s 	 e a c h .
e ) 	 Q u e s t i o n s 	 1 1 	 t o 	 2 2 	 c a r r y 	 t h r e e 	 m a r k s 	 e a c h .
f ) 	 Q u e s t i o n s 	 2 3 	 i s 	 v a l u e 	 b a s e d 	 q u e s t i o n 	 c a r r y i n g 	 f o u r 	 m a r k s .
g ) 	 Q u e s t i o n s 	 2 4 	 t o 	 2 6 	 c a r r y 	 f i v e 	 m a r k s 	 e a c h .
h ) 	 T h e r e 	 i s 	 n o 	 o v e r a l l 	 c h o i c e . 	 H o w e v e r , 	 a n 	 i n t e r n a l 	 c h o i c e 	 h a s 	 b e e n 	 p r o v i d e d 	 i n 	 o n e 	 q u e s t i o n
o f 	 t w o 	 m a r k s , 	 o n e 	 q u e s t i o n 	 o f 	 t h r e e 	 m a r k s 	 a n d 	 a l l 	 t h r e e 	 q u e s t i o n s 	 i n 	 f i v e 	 m a r k s 	 e a c h . 	 Y o u
h a v e 	 t o 	 a t t e m p t 	 o n l y 	 o n e 	 o f 	 t h e 	 c h o i c e s 	 i n 	 s u c h 	 q u e s t i o n s .
i ) 	 U s e 	 o f 	 c a l c u l a t o r s 	 i s 	 n o t 	 p e r m i t t e d . 	 H o w e v e r , 	 y o u 	 m a y 	 u s e 	 l o g 	 t a b l e s 	 i f 	 n e c e s s a r y .
1 . 	 D r a w 	 t h e 	 s t r u c t u r e 	 o f
a ) 	 2 , 3 - D i m e t h y l p e n t a n e
b ) 	 4 - P h e n y l b u t - 1 - e n e
A n s .
2 . 	 I f 	 a 	 t a n k 	 i s 	 f u l l 	 o f 	 w a t e r 	 c o m i n g 	 i n 	 a n d 	 o u t 	 a t 	 t h e 	 s a m e 	 r a t e , 	 t h e n 	 w h a t 	 w i l l 	 h a p p e n 	 t o
t h e 	 l e v e l 	 o f 	 w a t e r 	 i n 	 a 	 t a n k ?
A n s . 	 I t 	 w i l l 	 r e m a i n 	 t h e 	 s a m e 	 b e c a u s e 	 t h e 	 r a t e 	 o f 	 i n f l o w 	 i s 	 e q u a l 	 t o 	 t h e 	 r a t e 	 o f 	 o u t f l o w . 	 T h i s
s t a t e 	 i s 	 c a l l e d 	 s t a t e 	 o f 	 e q u i l i b r i u m .
3 . 	 E x p r e s s 	 3 2 . 3 9 2 8 0 0 	 t o 	 f o u r 	 s i g n i f i c a n t 	 f i g u r e s .
A n s . 	 3 2 . 9 3 .
4 . 	 W r i t e 	 t h e 	 c o r r e c t 	 s y m b o l 	 f o r 	 t h e 	 n u c l e u s 	 w i t h :
i . 	 A t o m i c 	 n u m b e r 	 5 6 	 a n d 	 m a s s 	 n u m b e r 	 1 3 8
i i . 	 A t o m i c 	 n u m b e r 	 2 6 	 a n d 	 m a s s 	 n u m b e r 	 5 5 .
A n s . 	 ( i ) 	
( i i ) 	
5 . 	 W h y 	 i s 	 G a 	 s m a l l e r 	 i n 	 s i z e 	 t h a n 	 A l ?
A n s . 	 D u e 	 t o 	 p o o r 	 s c r e e n i n g 	 e f f e c t 	 o f 	 1 0 	 d 	 e l e c t r o n s , 	 e f f e c t i v e 	 n u c l e a r 	 c h a r g e 	 i n 	 G a 	 i n c r e a s e s
l e a d i n g 	 t o 	 d e c r e a s e 	 i n 	 s i z e .
6 . 	 ( a ) 	 N a m e 	 t h e 	 e n e r g y 	 w h i c h 	 a r i s e s 	 d u e 	 t o 	 m o t i o n 	 o f 	 a t o m s 	 o r 	 m o l e c u l e s 	 i n 	 a 	 b o d y .
( b ) 	 H o w 	 i s 	 t h i s 	 e n e r g y 	 a f f e c t e d 	 w h e n 	 t h e 	 t e m p e r a t u r e 	 i s 	 i n c r e a s e d ?
O r
G i v e 	 t h e 	 r e l a t i o n s h i p 	 b e t w e e n 	 i s o t h e r m a l 	 a n d 	 f r e e 	 e x p a n s i o n 	 o f 	 a n 	 i d e a l 	 g a s .
A n s . 	 ( a ) 	 K i n e t i c 	 e n e r g y .
( b ) 	 I t 	 i n c r e a s e s 	 w i t h 	 i n c r e a s e 	 i n 	 t e m p e r a t u r e .
O r
W o r k 	 d o n e 	 i n 	 i s o t h e r m a l 	 r e v e r s i b l e 	 e x p a n s i o n 	 o f 	 a n 	 i d e a l 	 g a s
W 	 = 	 – 	 2 . 3 0 3 	 n R T 	 l o g 	 V
2
/ V
1
	 = 	 – 	 2 . 3 0 3 	 n R T 	 l o g 	 P
1
/ P
2
I n 	 t h e 	 f r e e 	 e x p a n s i o n 	 o f 	 a n 	 i d e a l 	 g a s , 	 w 	 = 	 0 	 b e c a u s e 	 i d e a l 	 g a s e s 	 h a v e 	 n e g l i g i b l e 	 f o r c e 	 o f
a t t r a c t i o n , 	 t h e r e f o r e 	 w o r k 	 d o n e 	 i s 	 z e r o 	 i n 	 f r e e 	 e x p a n s i o n 	 b e c a u s e 	 n o 	 e x t e r n a l 	 f o r c e 	 i s 	 a c t i n g .
W 	 = 	 - 	 P
e x t
V
P
e x t
	 = 	 0 ; 	 w 	 = 	 0
Page 3


C B S E 	 C l a s s 	 – 	 X I
C H E M I S T R Y
T i m e 	 a l l o w e d : 	 3 	 h o u r s , 	 M a x i m u m 	 M a r k s : 	 7 0
G e n e r a l 	 I n s t r u c t i o n s :
a ) 	 A l l 	 t h e 	 q u e s t i o n s 	 a r e 	 c o m p u l s o r y .
b ) 	 T h e r e 	 a r e 	 2 6 	 q u e s t i o n s 	 i n 	 t o t a l .
c ) 	 Q u e s t i o n s 	 1 	 t o 	 5 	 a r e 	 v e r y 	 s h o r t 	 a n s w e r 	 t y p e 	 q u e s t i o n s 	 a n d 	 c a r r y 	 o n e 	 m a r k 	 e a c h .
d ) 	 Q u e s t i o n s 	 6 	 t o 	 1 0 	 c a r r y 	 t w o 	 m a r k s 	 e a c h .
e ) 	 Q u e s t i o n s 	 1 1 	 t o 	 2 2 	 c a r r y 	 t h r e e 	 m a r k s 	 e a c h .
f ) 	 Q u e s t i o n s 	 2 3 	 i s 	 v a l u e 	 b a s e d 	 q u e s t i o n 	 c a r r y i n g 	 f o u r 	 m a r k s .
g ) 	 Q u e s t i o n s 	 2 4 	 t o 	 2 6 	 c a r r y 	 f i v e 	 m a r k s 	 e a c h .
h ) 	 T h e r e 	 i s 	 n o 	 o v e r a l l 	 c h o i c e . 	 H o w e v e r , 	 a n 	 i n t e r n a l 	 c h o i c e 	 h a s 	 b e e n 	 p r o v i d e d 	 i n 	 o n e 	 q u e s t i o n
o f 	 t w o 	 m a r k s , 	 o n e 	 q u e s t i o n 	 o f 	 t h r e e 	 m a r k s 	 a n d 	 a l l 	 t h r e e 	 q u e s t i o n s 	 i n 	 f i v e 	 m a r k s 	 e a c h . 	 Y o u
h a v e 	 t o 	 a t t e m p t 	 o n l y 	 o n e 	 o f 	 t h e 	 c h o i c e s 	 i n 	 s u c h 	 q u e s t i o n s .
i ) 	 U s e 	 o f 	 c a l c u l a t o r s 	 i s 	 n o t 	 p e r m i t t e d . 	 H o w e v e r , 	 y o u 	 m a y 	 u s e 	 l o g 	 t a b l e s 	 i f 	 n e c e s s a r y .
1 . 	 D r a w 	 t h e 	 s t r u c t u r e 	 o f
a ) 	 2 , 3 - D i m e t h y l p e n t a n e
b ) 	 4 - P h e n y l b u t - 1 - e n e
A n s .
2 . 	 I f 	 a 	 t a n k 	 i s 	 f u l l 	 o f 	 w a t e r 	 c o m i n g 	 i n 	 a n d 	 o u t 	 a t 	 t h e 	 s a m e 	 r a t e , 	 t h e n 	 w h a t 	 w i l l 	 h a p p e n 	 t o
t h e 	 l e v e l 	 o f 	 w a t e r 	 i n 	 a 	 t a n k ?
A n s . 	 I t 	 w i l l 	 r e m a i n 	 t h e 	 s a m e 	 b e c a u s e 	 t h e 	 r a t e 	 o f 	 i n f l o w 	 i s 	 e q u a l 	 t o 	 t h e 	 r a t e 	 o f 	 o u t f l o w . 	 T h i s
s t a t e 	 i s 	 c a l l e d 	 s t a t e 	 o f 	 e q u i l i b r i u m .
3 . 	 E x p r e s s 	 3 2 . 3 9 2 8 0 0 	 t o 	 f o u r 	 s i g n i f i c a n t 	 f i g u r e s .
A n s . 	 3 2 . 9 3 .
4 . 	 W r i t e 	 t h e 	 c o r r e c t 	 s y m b o l 	 f o r 	 t h e 	 n u c l e u s 	 w i t h :
i . 	 A t o m i c 	 n u m b e r 	 5 6 	 a n d 	 m a s s 	 n u m b e r 	 1 3 8
i i . 	 A t o m i c 	 n u m b e r 	 2 6 	 a n d 	 m a s s 	 n u m b e r 	 5 5 .
A n s . 	 ( i ) 	
( i i ) 	
5 . 	 W h y 	 i s 	 G a 	 s m a l l e r 	 i n 	 s i z e 	 t h a n 	 A l ?
A n s . 	 D u e 	 t o 	 p o o r 	 s c r e e n i n g 	 e f f e c t 	 o f 	 1 0 	 d 	 e l e c t r o n s , 	 e f f e c t i v e 	 n u c l e a r 	 c h a r g e 	 i n 	 G a 	 i n c r e a s e s
l e a d i n g 	 t o 	 d e c r e a s e 	 i n 	 s i z e .
6 . 	 ( a ) 	 N a m e 	 t h e 	 e n e r g y 	 w h i c h 	 a r i s e s 	 d u e 	 t o 	 m o t i o n 	 o f 	 a t o m s 	 o r 	 m o l e c u l e s 	 i n 	 a 	 b o d y .
( b ) 	 H o w 	 i s 	 t h i s 	 e n e r g y 	 a f f e c t e d 	 w h e n 	 t h e 	 t e m p e r a t u r e 	 i s 	 i n c r e a s e d ?
O r
G i v e 	 t h e 	 r e l a t i o n s h i p 	 b e t w e e n 	 i s o t h e r m a l 	 a n d 	 f r e e 	 e x p a n s i o n 	 o f 	 a n 	 i d e a l 	 g a s .
A n s . 	 ( a ) 	 K i n e t i c 	 e n e r g y .
( b ) 	 I t 	 i n c r e a s e s 	 w i t h 	 i n c r e a s e 	 i n 	 t e m p e r a t u r e .
O r
W o r k 	 d o n e 	 i n 	 i s o t h e r m a l 	 r e v e r s i b l e 	 e x p a n s i o n 	 o f 	 a n 	 i d e a l 	 g a s
W 	 = 	 – 	 2 . 3 0 3 	 n R T 	 l o g 	 V
2
/ V
1
	 = 	 – 	 2 . 3 0 3 	 n R T 	 l o g 	 P
1
/ P
2
I n 	 t h e 	 f r e e 	 e x p a n s i o n 	 o f 	 a n 	 i d e a l 	 g a s , 	 w 	 = 	 0 	 b e c a u s e 	 i d e a l 	 g a s e s 	 h a v e 	 n e g l i g i b l e 	 f o r c e 	 o f
a t t r a c t i o n , 	 t h e r e f o r e 	 w o r k 	 d o n e 	 i s 	 z e r o 	 i n 	 f r e e 	 e x p a n s i o n 	 b e c a u s e 	 n o 	 e x t e r n a l 	 f o r c e 	 i s 	 a c t i n g .
W 	 = 	 - 	 P
e x t
V
P
e x t
	 = 	 0 ; 	 w 	 = 	 0
7 . 	 P r e d i c t 	 t h e 	 f o r m u l a e 	 o f 	 t h e 	 s t a b l e 	 b i n a r y 	 c o m p o u n d s 	 t h a t 	 w o u l d 	 b e 	 f o r m e d 	 b y 	 t h e
c o m b i n a t i o n 	 o f 	 t h e 	 f o l l o w i n g 	 p a i r s 	 o f 	 e l e m e n t s :
a ) 	 E l e m e n t 	 7 1 	 a n d 	 F
b ) 	 A l 	 a n d 	 I
c ) 	 S i 	 a n d 	 O
d ) 	 P 	 a n d 	 F .
A n s . 	 ( a ) 	 L u F
3
( b ) 	 A l I
3
( c ) 	 S i O
2
( d ) 	 P F
5
8 . 	 W h y 	 t h e 	 b o t t l e 	 c o n t a i n i n g 	 h y d r o g e n 	 p e r o x i d e 	 s h o u l d 	 b e 	 c o o l e d 	 b e f o r e 	 o p e n i n g ?
A n s . 	 H y d r o g e n 	 p e r o x i d e 	 i s 	 u n s t a b l e 	 a n d 	 s o 	 d e c o m p o s e s 	 i n 	 w a t e r 	 a n d 	 o x y g e n 	 o n 	 l o n g
s t a n d i n g 	 o r 	 h e a t i n g . 	 H e n c e 	 t o 	 l o w e r 	 t h e 	 v a p o u r 	 p r e s s u r e 	 i n s i d e 	 t h e 	 b o t t l e , 	 i t 	 i s 	 c o o l e d 	 b e f o r e
o p e n i n g .
9 . 	 W h y 	 B e 	 a n d 	 M g 	 d o e s 	 n o t 	 g i v e 	 c o l o u r 	 t o 	 f l a m e 	 t h a n 	 t h e 	 a l k a l i n e 	 e a r t h 	 m e t a l s ?
A n s . 	 D u e 	 t o 	 s m a l l 	 s i z e , 	 t h e 	 i o n i z a t i o n 	 e n e r g y 	 o f 	 B e 	 a n d 	 M g 	 a r e 	 m u c h 	 h i g h e r 	 t h a n 	 a l k a l i n e
e a r t h 	 m e t a l s . 	 S o 	 t h e y 	 n e e d 	 l a r g e 	 a m o u n t 	 o f 	 e n e r g y 	 f o r 	 e x c i t a t i o n 	 o f 	 e l e c t r o n s 	 t o 	 h i g h e r
e n e r g y 	 l e v e l s . 	 T h i s 	 e n e r g y 	 i s 	 n o t 	 a v a i l a b l e 	 i n 	 B u n s e n 	 f l a m e 	 a n d 	 s o 	 d o 	 n o t 	 i m p a r t 	 a n y 	 c o l o u r
t o 	 t h e 	 f l a m e .
1 0 . 	 C a l c u l a t e 	 t h e 	 m o l a l i t y 	 o f 	 t h e 	 s o l u t i o n 	 i f 	 t h e 	 d e n s i t y 	 o f 	 3 M 	 s o l u t i o n 	 o f 	 N a C l 	 i s
1 . 2 5 g / m L .
A n s . 	 M o l a r i t y 	 = 	 3 M
D e n s i t y 	 = 	 1 . 2 5 g / m L
M a s s 	 o f 	 N a C l 	 i n 	 1 L 	 s o l u t i o n
= 	 M o l a r i t y 	 x 	 m o l a r 	 m a s s 	 = 	 3 	 x 	 5 8 . 5 	 = 	 1 7 5 . 5 g
D e n s i t y 	 = 	
M a s s 	 o f 	 1 L 	 N a C l 	 s o l u t i o n 	 = 	 1 . 2 5 	 x 	 1 0 0 0 	 = 	 1 2 5 0 g
M a s s 	 o f 	 w a t e r 	 i n 	 s o l u t i o n
= 	 1 2 5 0 - 1 7 5 . 5 	 = 	 1 0 7 4 . 5 g 	 = 	 1 . 0 7 4 5 	 k g
Page 4


C B S E 	 C l a s s 	 – 	 X I
C H E M I S T R Y
T i m e 	 a l l o w e d : 	 3 	 h o u r s , 	 M a x i m u m 	 M a r k s : 	 7 0
G e n e r a l 	 I n s t r u c t i o n s :
a ) 	 A l l 	 t h e 	 q u e s t i o n s 	 a r e 	 c o m p u l s o r y .
b ) 	 T h e r e 	 a r e 	 2 6 	 q u e s t i o n s 	 i n 	 t o t a l .
c ) 	 Q u e s t i o n s 	 1 	 t o 	 5 	 a r e 	 v e r y 	 s h o r t 	 a n s w e r 	 t y p e 	 q u e s t i o n s 	 a n d 	 c a r r y 	 o n e 	 m a r k 	 e a c h .
d ) 	 Q u e s t i o n s 	 6 	 t o 	 1 0 	 c a r r y 	 t w o 	 m a r k s 	 e a c h .
e ) 	 Q u e s t i o n s 	 1 1 	 t o 	 2 2 	 c a r r y 	 t h r e e 	 m a r k s 	 e a c h .
f ) 	 Q u e s t i o n s 	 2 3 	 i s 	 v a l u e 	 b a s e d 	 q u e s t i o n 	 c a r r y i n g 	 f o u r 	 m a r k s .
g ) 	 Q u e s t i o n s 	 2 4 	 t o 	 2 6 	 c a r r y 	 f i v e 	 m a r k s 	 e a c h .
h ) 	 T h e r e 	 i s 	 n o 	 o v e r a l l 	 c h o i c e . 	 H o w e v e r , 	 a n 	 i n t e r n a l 	 c h o i c e 	 h a s 	 b e e n 	 p r o v i d e d 	 i n 	 o n e 	 q u e s t i o n
o f 	 t w o 	 m a r k s , 	 o n e 	 q u e s t i o n 	 o f 	 t h r e e 	 m a r k s 	 a n d 	 a l l 	 t h r e e 	 q u e s t i o n s 	 i n 	 f i v e 	 m a r k s 	 e a c h . 	 Y o u
h a v e 	 t o 	 a t t e m p t 	 o n l y 	 o n e 	 o f 	 t h e 	 c h o i c e s 	 i n 	 s u c h 	 q u e s t i o n s .
i ) 	 U s e 	 o f 	 c a l c u l a t o r s 	 i s 	 n o t 	 p e r m i t t e d . 	 H o w e v e r , 	 y o u 	 m a y 	 u s e 	 l o g 	 t a b l e s 	 i f 	 n e c e s s a r y .
1 . 	 D r a w 	 t h e 	 s t r u c t u r e 	 o f
a ) 	 2 , 3 - D i m e t h y l p e n t a n e
b ) 	 4 - P h e n y l b u t - 1 - e n e
A n s .
2 . 	 I f 	 a 	 t a n k 	 i s 	 f u l l 	 o f 	 w a t e r 	 c o m i n g 	 i n 	 a n d 	 o u t 	 a t 	 t h e 	 s a m e 	 r a t e , 	 t h e n 	 w h a t 	 w i l l 	 h a p p e n 	 t o
t h e 	 l e v e l 	 o f 	 w a t e r 	 i n 	 a 	 t a n k ?
A n s . 	 I t 	 w i l l 	 r e m a i n 	 t h e 	 s a m e 	 b e c a u s e 	 t h e 	 r a t e 	 o f 	 i n f l o w 	 i s 	 e q u a l 	 t o 	 t h e 	 r a t e 	 o f 	 o u t f l o w . 	 T h i s
s t a t e 	 i s 	 c a l l e d 	 s t a t e 	 o f 	 e q u i l i b r i u m .
3 . 	 E x p r e s s 	 3 2 . 3 9 2 8 0 0 	 t o 	 f o u r 	 s i g n i f i c a n t 	 f i g u r e s .
A n s . 	 3 2 . 9 3 .
4 . 	 W r i t e 	 t h e 	 c o r r e c t 	 s y m b o l 	 f o r 	 t h e 	 n u c l e u s 	 w i t h :
i . 	 A t o m i c 	 n u m b e r 	 5 6 	 a n d 	 m a s s 	 n u m b e r 	 1 3 8
i i . 	 A t o m i c 	 n u m b e r 	 2 6 	 a n d 	 m a s s 	 n u m b e r 	 5 5 .
A n s . 	 ( i ) 	
( i i ) 	
5 . 	 W h y 	 i s 	 G a 	 s m a l l e r 	 i n 	 s i z e 	 t h a n 	 A l ?
A n s . 	 D u e 	 t o 	 p o o r 	 s c r e e n i n g 	 e f f e c t 	 o f 	 1 0 	 d 	 e l e c t r o n s , 	 e f f e c t i v e 	 n u c l e a r 	 c h a r g e 	 i n 	 G a 	 i n c r e a s e s
l e a d i n g 	 t o 	 d e c r e a s e 	 i n 	 s i z e .
6 . 	 ( a ) 	 N a m e 	 t h e 	 e n e r g y 	 w h i c h 	 a r i s e s 	 d u e 	 t o 	 m o t i o n 	 o f 	 a t o m s 	 o r 	 m o l e c u l e s 	 i n 	 a 	 b o d y .
( b ) 	 H o w 	 i s 	 t h i s 	 e n e r g y 	 a f f e c t e d 	 w h e n 	 t h e 	 t e m p e r a t u r e 	 i s 	 i n c r e a s e d ?
O r
G i v e 	 t h e 	 r e l a t i o n s h i p 	 b e t w e e n 	 i s o t h e r m a l 	 a n d 	 f r e e 	 e x p a n s i o n 	 o f 	 a n 	 i d e a l 	 g a s .
A n s . 	 ( a ) 	 K i n e t i c 	 e n e r g y .
( b ) 	 I t 	 i n c r e a s e s 	 w i t h 	 i n c r e a s e 	 i n 	 t e m p e r a t u r e .
O r
W o r k 	 d o n e 	 i n 	 i s o t h e r m a l 	 r e v e r s i b l e 	 e x p a n s i o n 	 o f 	 a n 	 i d e a l 	 g a s
W 	 = 	 – 	 2 . 3 0 3 	 n R T 	 l o g 	 V
2
/ V
1
	 = 	 – 	 2 . 3 0 3 	 n R T 	 l o g 	 P
1
/ P
2
I n 	 t h e 	 f r e e 	 e x p a n s i o n 	 o f 	 a n 	 i d e a l 	 g a s , 	 w 	 = 	 0 	 b e c a u s e 	 i d e a l 	 g a s e s 	 h a v e 	 n e g l i g i b l e 	 f o r c e 	 o f
a t t r a c t i o n , 	 t h e r e f o r e 	 w o r k 	 d o n e 	 i s 	 z e r o 	 i n 	 f r e e 	 e x p a n s i o n 	 b e c a u s e 	 n o 	 e x t e r n a l 	 f o r c e 	 i s 	 a c t i n g .
W 	 = 	 - 	 P
e x t
V
P
e x t
	 = 	 0 ; 	 w 	 = 	 0
7 . 	 P r e d i c t 	 t h e 	 f o r m u l a e 	 o f 	 t h e 	 s t a b l e 	 b i n a r y 	 c o m p o u n d s 	 t h a t 	 w o u l d 	 b e 	 f o r m e d 	 b y 	 t h e
c o m b i n a t i o n 	 o f 	 t h e 	 f o l l o w i n g 	 p a i r s 	 o f 	 e l e m e n t s :
a ) 	 E l e m e n t 	 7 1 	 a n d 	 F
b ) 	 A l 	 a n d 	 I
c ) 	 S i 	 a n d 	 O
d ) 	 P 	 a n d 	 F .
A n s . 	 ( a ) 	 L u F
3
( b ) 	 A l I
3
( c ) 	 S i O
2
( d ) 	 P F
5
8 . 	 W h y 	 t h e 	 b o t t l e 	 c o n t a i n i n g 	 h y d r o g e n 	 p e r o x i d e 	 s h o u l d 	 b e 	 c o o l e d 	 b e f o r e 	 o p e n i n g ?
A n s . 	 H y d r o g e n 	 p e r o x i d e 	 i s 	 u n s t a b l e 	 a n d 	 s o 	 d e c o m p o s e s 	 i n 	 w a t e r 	 a n d 	 o x y g e n 	 o n 	 l o n g
s t a n d i n g 	 o r 	 h e a t i n g . 	 H e n c e 	 t o 	 l o w e r 	 t h e 	 v a p o u r 	 p r e s s u r e 	 i n s i d e 	 t h e 	 b o t t l e , 	 i t 	 i s 	 c o o l e d 	 b e f o r e
o p e n i n g .
9 . 	 W h y 	 B e 	 a n d 	 M g 	 d o e s 	 n o t 	 g i v e 	 c o l o u r 	 t o 	 f l a m e 	 t h a n 	 t h e 	 a l k a l i n e 	 e a r t h 	 m e t a l s ?
A n s . 	 D u e 	 t o 	 s m a l l 	 s i z e , 	 t h e 	 i o n i z a t i o n 	 e n e r g y 	 o f 	 B e 	 a n d 	 M g 	 a r e 	 m u c h 	 h i g h e r 	 t h a n 	 a l k a l i n e
e a r t h 	 m e t a l s . 	 S o 	 t h e y 	 n e e d 	 l a r g e 	 a m o u n t 	 o f 	 e n e r g y 	 f o r 	 e x c i t a t i o n 	 o f 	 e l e c t r o n s 	 t o 	 h i g h e r
e n e r g y 	 l e v e l s . 	 T h i s 	 e n e r g y 	 i s 	 n o t 	 a v a i l a b l e 	 i n 	 B u n s e n 	 f l a m e 	 a n d 	 s o 	 d o 	 n o t 	 i m p a r t 	 a n y 	 c o l o u r
t o 	 t h e 	 f l a m e .
1 0 . 	 C a l c u l a t e 	 t h e 	 m o l a l i t y 	 o f 	 t h e 	 s o l u t i o n 	 i f 	 t h e 	 d e n s i t y 	 o f 	 3 M 	 s o l u t i o n 	 o f 	 N a C l 	 i s
1 . 2 5 g / m L .
A n s . 	 M o l a r i t y 	 = 	 3 M
D e n s i t y 	 = 	 1 . 2 5 g / m L
M a s s 	 o f 	 N a C l 	 i n 	 1 L 	 s o l u t i o n
= 	 M o l a r i t y 	 x 	 m o l a r 	 m a s s 	 = 	 3 	 x 	 5 8 . 5 	 = 	 1 7 5 . 5 g
D e n s i t y 	 = 	
M a s s 	 o f 	 1 L 	 N a C l 	 s o l u t i o n 	 = 	 1 . 2 5 	 x 	 1 0 0 0 	 = 	 1 2 5 0 g
M a s s 	 o f 	 w a t e r 	 i n 	 s o l u t i o n
= 	 1 2 5 0 - 1 7 5 . 5 	 = 	 1 0 7 4 . 5 g 	 = 	 1 . 0 7 4 5 	 k g
M o l a l i t y 	 = 	
= 	 	 = 	 2 . 7 9 	 m
1 1 . 	 ( a ) 	 G i v e 	 t h e 	 i m p o r t a n c e 	 o f 	 m e a s u r i n g 	 B O D 	 o f 	 a 	 w a t e r 	 b o d y .
( b ) 	 W h a t 	 i s 	 d e s i r a b l e 	 c o n c e n t r a t i o n 	 o f 	 f l u o r i d e 	 i o n 	 p H 	 o f 	 d r i n k i n g 	 w a t e r ?
( c ) 	 G i v e 	 t h e 	 h a r m f u l 	 e f f e c t 	 o f 	 n i t r o g e n 	 d i o x i d e .
A n s . 	 ( a ) 	 B O D 	 i s 	 a 	 m e a s u r e 	 o f 	 l e v e l 	 o f 	 p o l l u t i o n 	 c a u s e d 	 b y 	 o r g a n i c 	 b i o d e g r a d a b l e 	 m a t e r i a l .
L o w 	 v a l u e 	 o f 	 B O D 	 m e a n s 	 w a t e r 	 i s 	 l e s s 	 p o l l u t e d .
( b ) 	 1 	 p p m 	 i s 	 d e s i r a b l e 	 c o n c e n t r a t i o n 	 o f 	 f l u o r i d e 	 i o n s 	 i n 	 d r i n k i n g 	 w a t e r . 	 T h e 	 p H 	 o f 	 d r i n k i n g
w a t e r 	 s h o u l d 	 b e 	 b e t w e e n 	 5 . 5 	 – 	 9 . 5 .
( c ) 	 N i t r o g e n 	 d i o x i d e 	 i s 	 e x t r e m e l y 	 t o x i c 	 t o 	 l i v i n g 	 t i s s u e s 	 a n d 	 h a r m f u l 	 t o 	 p l a n t s , 	 p a i n t s , 	 t e x t i l e s
a n d 	 m e t a l s . 	 I t 	 c a u s e s 	 a c i d 	 r a i n . 	 I t 	 p r o d u c e s 	 p h o t o c h e m i c a l 	 s m o g .
1 2 . 	 ( a ) 	 D e f i n e :
i ) 	 I n t e n s i v e 	 p r o p e r t i e s
i i ) 	 A d i a b a t i c 	 p r o c e s s
( b ) 	 D e r i v e 	 G = – T S
t o t a l
	 f r o m 	 t h e 	 r e l a t i o n s h i p 	 G = H 	 – 	 T S .
A n s . 	 ( a )
i ) 	 T h e 	 p r o p e r t i e s 	 w h i c h 	 d e p e n d 	 o n l y 	 o n 	 t h e 	 n a t u r e 	 o f 	 t h e 	 s u b s t a n c e 	 a n d 	 n o t 	 o n 	 t h e 	 a m o u n t 	 o f
t h e 	 s u b s t a n c e 	 a r e 	 c a l l e d 	 i n t e n s i v e 	 p r o p e r t i e s . 	 E x a m p l e : 	 D e n s i t y .
i i ) 	 A 	 p r o c e s s 	 i n 	 w h i c h 	 n o 	 h e a t 	 f l o w s 	 b e t w e e n 	 t h e 	 s y s t e m 	 a n d 	 t h e 	 s u r r o u n d i n g s 	 i s 	 c a l l e d 	 a n
a d i a b a t i c 	 p r o c e s s 	 i . e . 	 q = 	 0 .
( b ) C h a n g e 	 i n 	 G i b b s 	 e n e r g y , 	 G = 	 G
2
	 – 	 G
1
,
E n t h a l p y 	 c h a n g e , 	 H = 	 H
2
	 – 	 H
1
,
E n t r o p y 	 c h a n g e , 	 S = 	 S
2
	 – 	 S
1
,
Page 5


C B S E 	 C l a s s 	 – 	 X I
C H E M I S T R Y
T i m e 	 a l l o w e d : 	 3 	 h o u r s , 	 M a x i m u m 	 M a r k s : 	 7 0
G e n e r a l 	 I n s t r u c t i o n s :
a ) 	 A l l 	 t h e 	 q u e s t i o n s 	 a r e 	 c o m p u l s o r y .
b ) 	 T h e r e 	 a r e 	 2 6 	 q u e s t i o n s 	 i n 	 t o t a l .
c ) 	 Q u e s t i o n s 	 1 	 t o 	 5 	 a r e 	 v e r y 	 s h o r t 	 a n s w e r 	 t y p e 	 q u e s t i o n s 	 a n d 	 c a r r y 	 o n e 	 m a r k 	 e a c h .
d ) 	 Q u e s t i o n s 	 6 	 t o 	 1 0 	 c a r r y 	 t w o 	 m a r k s 	 e a c h .
e ) 	 Q u e s t i o n s 	 1 1 	 t o 	 2 2 	 c a r r y 	 t h r e e 	 m a r k s 	 e a c h .
f ) 	 Q u e s t i o n s 	 2 3 	 i s 	 v a l u e 	 b a s e d 	 q u e s t i o n 	 c a r r y i n g 	 f o u r 	 m a r k s .
g ) 	 Q u e s t i o n s 	 2 4 	 t o 	 2 6 	 c a r r y 	 f i v e 	 m a r k s 	 e a c h .
h ) 	 T h e r e 	 i s 	 n o 	 o v e r a l l 	 c h o i c e . 	 H o w e v e r , 	 a n 	 i n t e r n a l 	 c h o i c e 	 h a s 	 b e e n 	 p r o v i d e d 	 i n 	 o n e 	 q u e s t i o n
o f 	 t w o 	 m a r k s , 	 o n e 	 q u e s t i o n 	 o f 	 t h r e e 	 m a r k s 	 a n d 	 a l l 	 t h r e e 	 q u e s t i o n s 	 i n 	 f i v e 	 m a r k s 	 e a c h . 	 Y o u
h a v e 	 t o 	 a t t e m p t 	 o n l y 	 o n e 	 o f 	 t h e 	 c h o i c e s 	 i n 	 s u c h 	 q u e s t i o n s .
i ) 	 U s e 	 o f 	 c a l c u l a t o r s 	 i s 	 n o t 	 p e r m i t t e d . 	 H o w e v e r , 	 y o u 	 m a y 	 u s e 	 l o g 	 t a b l e s 	 i f 	 n e c e s s a r y .
1 . 	 D r a w 	 t h e 	 s t r u c t u r e 	 o f
a ) 	 2 , 3 - D i m e t h y l p e n t a n e
b ) 	 4 - P h e n y l b u t - 1 - e n e
A n s .
2 . 	 I f 	 a 	 t a n k 	 i s 	 f u l l 	 o f 	 w a t e r 	 c o m i n g 	 i n 	 a n d 	 o u t 	 a t 	 t h e 	 s a m e 	 r a t e , 	 t h e n 	 w h a t 	 w i l l 	 h a p p e n 	 t o
t h e 	 l e v e l 	 o f 	 w a t e r 	 i n 	 a 	 t a n k ?
A n s . 	 I t 	 w i l l 	 r e m a i n 	 t h e 	 s a m e 	 b e c a u s e 	 t h e 	 r a t e 	 o f 	 i n f l o w 	 i s 	 e q u a l 	 t o 	 t h e 	 r a t e 	 o f 	 o u t f l o w . 	 T h i s
s t a t e 	 i s 	 c a l l e d 	 s t a t e 	 o f 	 e q u i l i b r i u m .
3 . 	 E x p r e s s 	 3 2 . 3 9 2 8 0 0 	 t o 	 f o u r 	 s i g n i f i c a n t 	 f i g u r e s .
A n s . 	 3 2 . 9 3 .
4 . 	 W r i t e 	 t h e 	 c o r r e c t 	 s y m b o l 	 f o r 	 t h e 	 n u c l e u s 	 w i t h :
i . 	 A t o m i c 	 n u m b e r 	 5 6 	 a n d 	 m a s s 	 n u m b e r 	 1 3 8
i i . 	 A t o m i c 	 n u m b e r 	 2 6 	 a n d 	 m a s s 	 n u m b e r 	 5 5 .
A n s . 	 ( i ) 	
( i i ) 	
5 . 	 W h y 	 i s 	 G a 	 s m a l l e r 	 i n 	 s i z e 	 t h a n 	 A l ?
A n s . 	 D u e 	 t o 	 p o o r 	 s c r e e n i n g 	 e f f e c t 	 o f 	 1 0 	 d 	 e l e c t r o n s , 	 e f f e c t i v e 	 n u c l e a r 	 c h a r g e 	 i n 	 G a 	 i n c r e a s e s
l e a d i n g 	 t o 	 d e c r e a s e 	 i n 	 s i z e .
6 . 	 ( a ) 	 N a m e 	 t h e 	 e n e r g y 	 w h i c h 	 a r i s e s 	 d u e 	 t o 	 m o t i o n 	 o f 	 a t o m s 	 o r 	 m o l e c u l e s 	 i n 	 a 	 b o d y .
( b ) 	 H o w 	 i s 	 t h i s 	 e n e r g y 	 a f f e c t e d 	 w h e n 	 t h e 	 t e m p e r a t u r e 	 i s 	 i n c r e a s e d ?
O r
G i v e 	 t h e 	 r e l a t i o n s h i p 	 b e t w e e n 	 i s o t h e r m a l 	 a n d 	 f r e e 	 e x p a n s i o n 	 o f 	 a n 	 i d e a l 	 g a s .
A n s . 	 ( a ) 	 K i n e t i c 	 e n e r g y .
( b ) 	 I t 	 i n c r e a s e s 	 w i t h 	 i n c r e a s e 	 i n 	 t e m p e r a t u r e .
O r
W o r k 	 d o n e 	 i n 	 i s o t h e r m a l 	 r e v e r s i b l e 	 e x p a n s i o n 	 o f 	 a n 	 i d e a l 	 g a s
W 	 = 	 – 	 2 . 3 0 3 	 n R T 	 l o g 	 V
2
/ V
1
	 = 	 – 	 2 . 3 0 3 	 n R T 	 l o g 	 P
1
/ P
2
I n 	 t h e 	 f r e e 	 e x p a n s i o n 	 o f 	 a n 	 i d e a l 	 g a s , 	 w 	 = 	 0 	 b e c a u s e 	 i d e a l 	 g a s e s 	 h a v e 	 n e g l i g i b l e 	 f o r c e 	 o f
a t t r a c t i o n , 	 t h e r e f o r e 	 w o r k 	 d o n e 	 i s 	 z e r o 	 i n 	 f r e e 	 e x p a n s i o n 	 b e c a u s e 	 n o 	 e x t e r n a l 	 f o r c e 	 i s 	 a c t i n g .
W 	 = 	 - 	 P
e x t
V
P
e x t
	 = 	 0 ; 	 w 	 = 	 0
7 . 	 P r e d i c t 	 t h e 	 f o r m u l a e 	 o f 	 t h e 	 s t a b l e 	 b i n a r y 	 c o m p o u n d s 	 t h a t 	 w o u l d 	 b e 	 f o r m e d 	 b y 	 t h e
c o m b i n a t i o n 	 o f 	 t h e 	 f o l l o w i n g 	 p a i r s 	 o f 	 e l e m e n t s :
a ) 	 E l e m e n t 	 7 1 	 a n d 	 F
b ) 	 A l 	 a n d 	 I
c ) 	 S i 	 a n d 	 O
d ) 	 P 	 a n d 	 F .
A n s . 	 ( a ) 	 L u F
3
( b ) 	 A l I
3
( c ) 	 S i O
2
( d ) 	 P F
5
8 . 	 W h y 	 t h e 	 b o t t l e 	 c o n t a i n i n g 	 h y d r o g e n 	 p e r o x i d e 	 s h o u l d 	 b e 	 c o o l e d 	 b e f o r e 	 o p e n i n g ?
A n s . 	 H y d r o g e n 	 p e r o x i d e 	 i s 	 u n s t a b l e 	 a n d 	 s o 	 d e c o m p o s e s 	 i n 	 w a t e r 	 a n d 	 o x y g e n 	 o n 	 l o n g
s t a n d i n g 	 o r 	 h e a t i n g . 	 H e n c e 	 t o 	 l o w e r 	 t h e 	 v a p o u r 	 p r e s s u r e 	 i n s i d e 	 t h e 	 b o t t l e , 	 i t 	 i s 	 c o o l e d 	 b e f o r e
o p e n i n g .
9 . 	 W h y 	 B e 	 a n d 	 M g 	 d o e s 	 n o t 	 g i v e 	 c o l o u r 	 t o 	 f l a m e 	 t h a n 	 t h e 	 a l k a l i n e 	 e a r t h 	 m e t a l s ?
A n s . 	 D u e 	 t o 	 s m a l l 	 s i z e , 	 t h e 	 i o n i z a t i o n 	 e n e r g y 	 o f 	 B e 	 a n d 	 M g 	 a r e 	 m u c h 	 h i g h e r 	 t h a n 	 a l k a l i n e
e a r t h 	 m e t a l s . 	 S o 	 t h e y 	 n e e d 	 l a r g e 	 a m o u n t 	 o f 	 e n e r g y 	 f o r 	 e x c i t a t i o n 	 o f 	 e l e c t r o n s 	 t o 	 h i g h e r
e n e r g y 	 l e v e l s . 	 T h i s 	 e n e r g y 	 i s 	 n o t 	 a v a i l a b l e 	 i n 	 B u n s e n 	 f l a m e 	 a n d 	 s o 	 d o 	 n o t 	 i m p a r t 	 a n y 	 c o l o u r
t o 	 t h e 	 f l a m e .
1 0 . 	 C a l c u l a t e 	 t h e 	 m o l a l i t y 	 o f 	 t h e 	 s o l u t i o n 	 i f 	 t h e 	 d e n s i t y 	 o f 	 3 M 	 s o l u t i o n 	 o f 	 N a C l 	 i s
1 . 2 5 g / m L .
A n s . 	 M o l a r i t y 	 = 	 3 M
D e n s i t y 	 = 	 1 . 2 5 g / m L
M a s s 	 o f 	 N a C l 	 i n 	 1 L 	 s o l u t i o n
= 	 M o l a r i t y 	 x 	 m o l a r 	 m a s s 	 = 	 3 	 x 	 5 8 . 5 	 = 	 1 7 5 . 5 g
D e n s i t y 	 = 	
M a s s 	 o f 	 1 L 	 N a C l 	 s o l u t i o n 	 = 	 1 . 2 5 	 x 	 1 0 0 0 	 = 	 1 2 5 0 g
M a s s 	 o f 	 w a t e r 	 i n 	 s o l u t i o n
= 	 1 2 5 0 - 1 7 5 . 5 	 = 	 1 0 7 4 . 5 g 	 = 	 1 . 0 7 4 5 	 k g
M o l a l i t y 	 = 	
= 	 	 = 	 2 . 7 9 	 m
1 1 . 	 ( a ) 	 G i v e 	 t h e 	 i m p o r t a n c e 	 o f 	 m e a s u r i n g 	 B O D 	 o f 	 a 	 w a t e r 	 b o d y .
( b ) 	 W h a t 	 i s 	 d e s i r a b l e 	 c o n c e n t r a t i o n 	 o f 	 f l u o r i d e 	 i o n 	 p H 	 o f 	 d r i n k i n g 	 w a t e r ?
( c ) 	 G i v e 	 t h e 	 h a r m f u l 	 e f f e c t 	 o f 	 n i t r o g e n 	 d i o x i d e .
A n s . 	 ( a ) 	 B O D 	 i s 	 a 	 m e a s u r e 	 o f 	 l e v e l 	 o f 	 p o l l u t i o n 	 c a u s e d 	 b y 	 o r g a n i c 	 b i o d e g r a d a b l e 	 m a t e r i a l .
L o w 	 v a l u e 	 o f 	 B O D 	 m e a n s 	 w a t e r 	 i s 	 l e s s 	 p o l l u t e d .
( b ) 	 1 	 p p m 	 i s 	 d e s i r a b l e 	 c o n c e n t r a t i o n 	 o f 	 f l u o r i d e 	 i o n s 	 i n 	 d r i n k i n g 	 w a t e r . 	 T h e 	 p H 	 o f 	 d r i n k i n g
w a t e r 	 s h o u l d 	 b e 	 b e t w e e n 	 5 . 5 	 – 	 9 . 5 .
( c ) 	 N i t r o g e n 	 d i o x i d e 	 i s 	 e x t r e m e l y 	 t o x i c 	 t o 	 l i v i n g 	 t i s s u e s 	 a n d 	 h a r m f u l 	 t o 	 p l a n t s , 	 p a i n t s , 	 t e x t i l e s
a n d 	 m e t a l s . 	 I t 	 c a u s e s 	 a c i d 	 r a i n . 	 I t 	 p r o d u c e s 	 p h o t o c h e m i c a l 	 s m o g .
1 2 . 	 ( a ) 	 D e f i n e :
i ) 	 I n t e n s i v e 	 p r o p e r t i e s
i i ) 	 A d i a b a t i c 	 p r o c e s s
( b ) 	 D e r i v e 	 G = – T S
t o t a l
	 f r o m 	 t h e 	 r e l a t i o n s h i p 	 G = H 	 – 	 T S .
A n s . 	 ( a )
i ) 	 T h e 	 p r o p e r t i e s 	 w h i c h 	 d e p e n d 	 o n l y 	 o n 	 t h e 	 n a t u r e 	 o f 	 t h e 	 s u b s t a n c e 	 a n d 	 n o t 	 o n 	 t h e 	 a m o u n t 	 o f
t h e 	 s u b s t a n c e 	 a r e 	 c a l l e d 	 i n t e n s i v e 	 p r o p e r t i e s . 	 E x a m p l e : 	 D e n s i t y .
i i ) 	 A 	 p r o c e s s 	 i n 	 w h i c h 	 n o 	 h e a t 	 f l o w s 	 b e t w e e n 	 t h e 	 s y s t e m 	 a n d 	 t h e 	 s u r r o u n d i n g s 	 i s 	 c a l l e d 	 a n
a d i a b a t i c 	 p r o c e s s 	 i . e . 	 q = 	 0 .
( b ) C h a n g e 	 i n 	 G i b b s 	 e n e r g y , 	 G = 	 G
2
	 – 	 G
1
,
E n t h a l p y 	 c h a n g e , 	 H = 	 H
2
	 – 	 H
1
,
E n t r o p y 	 c h a n g e , 	 S = 	 S
2
	 – 	 S
1
,
T S
t o t a l
	 = 	 T S 	 – 	 H
T S
t o t a l
	 = 	 H 	 - 	 T S 	 = 	 G
T h e r e f o r e , 	 G 	 = 	 - 	 T S
t o t a l
1 3 . 	 W e 	 k n o w 	 t h a t 	 7 5 % 	 o f 	 s o l a r 	 e n e r g y 	 r e a c h i n g 	 t h e 	 e a r t h , 	 i s 	 a b s o r b e d 	 b y 	 e a r t h ’ s 	 s u r f a c e
i n c r e a s e s 	 i t s 	 t e m p e r a t u r e . 	 T h e 	 r e s t 	 o f 	 h e a t 	 r a d i a t e s 	 b a c k 	 t o 	 t h e 	 a t m o s p h e r e . 	 S o m e 	 o f
t h e 	 h e a t 	 i s 	 t r a p p e d 	 b y 	 g a s e s 	 s u c h 	 a s 	 C O , 	 C H
4
, 	 O
3
, 	 C F C ’ s 	 a n d 	 w a t e r 	 v a p o u r s 	 p r e s e n t 	 i n 	 t h e
a t m o s p h e r e . 	 T h i s 	 c a u s e s 	 g l o b a l 	 w a r m i n g .
a ) 	 S u g g e s t 	 s o m e 	 m e a s u r e s 	 t o 	 d e c r e a s e 	 C O 	 g a s 	 i n 	 t h e 	 a t m o s p h e r e .
b ) 	 G i v e 	 a 	 m e t h o d 	 t o 	 s a v e 	 o z o n e 	 l a y e r .
c ) 	 W i l l 	 t h e 	 u s e 	 o f 	 s o l a r 	 e n e r g y 	 s o l v e 	 o u r 	 p r o b l e m s ? 	 C o m m e n t .
A n s . 	 ( a ) 	 U s i n g 	 C N G 	 a s 	 a 	 f u e l , 	 u s i n g 	 p u b l i c 	 t r a n s p o r t s , 	 e l e c t r i c 	 c a r s 	 a n d 	 b i c y c l e s 	 a n d 	 a v o i d i n g
b u r n i n g 	 o f 	 d r y 	 l e a v e s , 	 p l a s t i c 	 b a g s 	 e t c .
( b ) 	 B a n n i n g 	 C F C s 	 u s e d 	 i n 	 r e f r i g e r a t o r s , 	 A C 	 e t c . , 	 a n d 	 u s i n g 	 l e s s 	 a m o u n t 	 o f 	 d i e s e l 	 a n d 	 p e t r o l .
( c ) 	 Y e s . 	 S o l a r 	 e n e r g y 	 r e d u c e s 	 p o l l u t i o n . 	 B y 	 m a k i n g 	 g r e e n 	 b u i l d i n g , 	 a 	 l o t 	 o f 	 n a t u r a l 	 l i g h t 	 a n d
n a t u r a l 	 c o o l i n g 	 a n d 	 h e a t i n g 	 t a k e s 	 p l a c e 	 w h i c h 	 s a v e 	 l o t 	 o f 	 e n e r g y 	 a n d 	 e n v i r o n m e n t .
1 4 . 	 C o m m e n t 	 o n 	 t h e 	 g r a p h 	 b e l o w .
A n s . 	 I t 	 r e p r e s e n t s 	 t h e 	 g r a p h 	 b e t w e e n 	 p 	 a n d 	 1 / V . 	 I t 	 i s 	 a 	 s t r a i g h t 	 l i n e 	 p a s s i n g 	 t h r o u g h 	 o r i g i n .
H o w e v e r 	 a t 	 h i g h 	 p r e s s u r e s , 	 g a s e s 	 d e v i a t e 	 f r o m 	 B o y l e ’ s 	 l a w 	 a n d 	 u n d e r 	 s u c h 	 c o n d i t i o n s 	 a
s t r a i g h t 	 l i n e 	 i s 	 n o t 	 o b t a i n e d 	 i n 	 t h e 	 g r a p h .
1 5 . 	 I f 	 t h e 	 d e n s i t y 	 o f 	 3 M 	 s o l u t i o n 	 o f 	 N a C l 	 i s 	 1 . 2 5 g / m L , 	 c a l c u l a t e 	 t h e 	 m o l a l i t y 	 o f 	 t h e
s o l u t i o n .
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FAQs on Past Year Paper with solution: Chemistry, 2018, Class 11 - Chemistry for Grade 11

1. What are the different types of chemical reactions?
2. How can I balance a chemical equation?
Ans. To balance a chemical equation, you need to ensure that the number of atoms of each element is the same on both sides of the equation. Start by identifying the unbalanced elements and adjust the coefficients in front of the compounds to balance the atoms. Begin with the most complex compounds and balance elements that appear in only one compound first. Use coefficients to adjust the number of atoms, but avoid changing subscripts. Balance hydrogen and oxygen last, using water and/or hydrogen ions. Continue adjusting coefficients until the equation is balanced.
3. What is stoichiometry in chemistry?
Ans. Stoichiometry is a branch of chemistry that deals with the quantitative relationships between reactants and products in chemical reactions. It allows us to determine the amounts of substances involved in a chemical reaction and predict the yield of products. Stoichiometry is based on the principle of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. By using balanced chemical equations, stoichiometry calculations can be performed to determine the ratios of reactants and products.
4. What is the difference between an exothermic and endothermic reaction?
Ans. An exothermic reaction is a chemical reaction that releases energy, usually in the form of heat, to the surroundings. In an exothermic reaction, the products have lower energy than the reactants, and the energy released is shown as a negative value in the reaction's enthalpy change (ΔH) value. On the other hand, an endothermic reaction is a chemical reaction that absorbs energy from the surroundings. In an endothermic reaction, the products have higher energy than the reactants, and the energy absorbed is shown as a positive value in the reaction's enthalpy change (ΔH) value.
5. How do catalysts affect chemical reactions?
Ans. Catalysts are substances that can increase the rate of a chemical reaction without being consumed in the process. They work by providing an alternative reaction pathway with a lower activation energy, allowing the reaction to occur more readily. Catalysts work by reducing the energy required for the reactants to reach the transition state, thus increasing the rate of the reaction. They do not change the overall enthalpy change or equilibrium position of the reaction. Catalysts can be used to speed up reactions in various industrial processes and are often specific to certain reactions.
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Document Description: Past Year Paper with solution: Chemistry, 2018, Class 11 for Grade 11 2025 is part of Chemistry for Grade 11 preparation. The notes and questions for Past Year Paper with solution: Chemistry, 2018, Class 11 have been prepared according to the Grade 11 exam syllabus. Information about Past Year Paper with solution: Chemistry, 2018, Class 11 covers topics like and Past Year Paper with solution: Chemistry, 2018, Class 11 Example, for Grade 11 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises and tests below for Past Year Paper with solution: Chemistry, 2018, Class 11.
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