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 .Read More
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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? |  |
Ans. There are several types of chemical reactions, including synthesis or combination reactions, decomposition reactions, displacement reactions, redox reactions, and acid-base reactions. In a synthesis reaction, two or more substances combine to form a new compound. Decomposition reactions involve the breakdown of a compound into simpler substances. Displacement reactions occur when one element replaces another in a compound. Redox reactions involve the transfer of electrons between species, while acid-base reactions involve the transfer of protons between acids and bases.
| 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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The content of Past Year Paper with solution: Chemistry, 2018, Class 11 is prepared as per the latest Grade 11 syllabus.
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