Topic 4: Formulas & Names. Equations. Moles- Equations ... · PDF fileDetermine the total...

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Transcript of Topic 4: Formulas & Names. Equations. Moles- Equations ... · PDF fileDetermine the total...

  • Topic 4: Formulas & Names. Equations. Moles-Molar Mass. & Types of Reactions Outline

    1. A compound is a substance composed of two or more different elements that are chemically combined in a fixed proportion. A chemical compound can only be broken down by chemical means.

    2. Chemical compounds can be represented by a specific formula and assigned a name based on the lUPAC system.

    3. Types of chemical formulas include empirical, molecular, and structural. ^ E m p i r i c a l f o r m u l a s s h o w e l e m e n t s in t h e i r s i m p l e s t w h o l e n u m b e r r a t i o s . T h i s m a y o r m a y

    n o t b e t h e s a m e a s t h e m o l e c u l a r f o r m u l a . ^ M o l e c u l a r f o r m u l a s s h o w t h e a c t u a l n u m b e r o f a t o m s p e r e l e m e n t in a s i n g l e m o l e c u l e . ^ S t r u c t u r a l f o r m u l a s s h o w t h e n u m b e r o f e a c h t y p e o f a t o m a s w e l l a s t h e i r p h y s i c a l

    a r r a n g e m e n t .

    4. All chemical reactions show a conservation of mass, energy and charge.

    5. A balanced chemical equation represents conservation of atoms.

    6. The coefficients in a balanced chemical equation can be used to determine mole ratios in the reaction, and can further be used to predict relationships about amounts between products and reactants.

    7. The molar mass of a substance is the sum of the atomic masses of its atoms. The molar mass (gram formula mass) equals the mass of one mole of that substance.

    8. The percent composition by mass of each element in a compound can be calculated mathematically.

    9. Types of chemical reactions include synthesis, decomposition, single replacement, and double replacement.

    25

    Equations & Stoichiometrv - Practice Questions

    1 . W h i c h s u b s t a n c e h a s t h e g r e a t e s t m o l e c u l a r m a s s ? (1 ) H 2 0 2 ( 2 ) N O ( 3 ) C F , ( 4 ) l 2

    2. W h a t is t h e g r a m f o r m u l a m a s s o f C a ( 0 H ) 2 ? ( l ) 2 9 g ( 2 ) 3 4 g ( 3 ) 5 7 g ( 4 ) 7 4 g

    3 . W h a t i s t h e t o t a l n u m b e r o f m o l e s o f a t o m s p r e s e n t in 1 g r a m f o r m u l a m a s s o f Pb(C2H302 ) 2 ? ( 1 ) 9 ( 2 ) 1 4 ( 3 ) 3 ( 4 ) 1 5

    4 . T h e p e r c e n t by m a s s o f c a r b o n in HC2H3O2 is e q u a l t o

    ( 1 ) x l O O ( 2 ) x l O O ( 3 ) ^ x 1 0 0 ( 4 ) ^ x 1 0 0 ^ ' 6 0 6 0 24 '12

    5. W h a t i s t h e e m p i r i c a l f o r m u l a o f C3H6? ( 1 ) C H (2 ) C H 2 ( 3 ) C H 3 ( 4 ) C H 6

    6 . T h e n a m e o f t h e c o m p o u n d KCIO2 i s p o t a s s i u m ( 1 ) h y p o c h l o r i t e ( 3 ) c h l o r a t e ( 2 ) c h l o r i t e ( 4 ) p e r c h l o r a t e

    7. W h i c h f o r m u l a i s c o r r e c t f o r a m m o n i u m s u l f a t e ? ( l ) N H 4 S 0 i ( 2 ) ( N H , ) 2 S 0 4 ( 3 ) N H , ( S 0 4 ) 2 ( 4 ) ( N H ) 3 ( S O , ) 2

    8. T h e m o l e c u l a r f o r m u l a o f a c o m p o u n d i s r e p r e s e n t e d b y X3Y6. W h a t is t h e e m p i r i c a l f o r m u l a o f t h i s c o m p o u n d ? ( 1 ) X 3 Y ( 2 ) X 2 Y ( 3 ) X Y 2 ( 4 ) X Y

    9 . T h e n u m b e r o f m o l e s o f m o l e c u l e s i n a 1 2 . 0 - g r a m s a m p l e s o f CI2 Is

    ( 1 ) m o l e ( 2 ) m o l e ( 3 ) 1 2 . 0 m o l e s ( 4 ) 1 2 . 0 x 3 5 . 5 m o l e s 35 .5 71 .0

    1 0 . W h a t i s t h e t o t a l n u m b e r o f m o l e s o f s u l f u r a t o m s in 1 m o l e o f F e 2 ( S 0 i ) 3 ? ( 1 ) 1 ( 2 ) 1 5 ( 3 ) 3 ( 4 ) 1 7

    1 1 . G i v e n t h e u n b a l a n c e d e q u a t i o n :

    CaSOi + AICI3 ^ Al2(S04)3 + CaCb

    W h a t is t h e c o e f f i c i e n t o f Al2 (S04)3 w h e n t h e e q u a t i o n Is c o m p l e t e l y b a l a n c e d u s i n g t h e s m a l l e s t w h o l e - n u m b e r c o e f f i c i e n t s ? ( 1 ) 1 (2)2 ( 3 ) 3 ( 4 ) 4

    26

  • 1 2 . G i v e n t h e u n b a l a n c e d e q u a t i o n ;

    Al (s) + O2 (g) ^ AI2O3 (s)

    W h e n t h i s e q u a t i o n i s c o r r e c t l y b a l a n c e d u s i n g s m a l l e s t w h o l e n u m b e r s , w h a t i s t h e c o e f f i c i e n t o f O2 ( g ) ? ( 1 ) 6 (2)2 ( 3 ) 3 ( 4 ) 4

    1 3 . G i v e n t h e r e a c t i o n :

    4 NH3 + 5 O2 -> 4 NO + 6 H2O

    W h a t is t h e to t a l n u m b e r o f m o l e s o f N O p r o d u c e d w h e n 1.0 m o l e o f O2 is c o m p l e t e l y c o n s u m e d ? ( 1 ) 1.0 m o l e ( 2 ) 1.2 m o l e s ( 3 ) 0 . 8 0 m o l e ( 4 ) 4 . 0 m o l e s

    1 4 . G i v e n t h e e q u a t i o n :

    H2 (g) + CI2 (g) ^ 2 HCI (g)

    W h a t is t h e t o t a l n u m b e r o f m o l e s o f HC I ( g ) p r o d u c e d w h e n 3 m o l e s o f H2 ( g ) i s c o m p l e t e l y c o n s u m e d ? ( 1 ) 5 m o l e s ( 2 ) 2 m o l e s ( 3 ) 3 m o l e s ( 4 ) 6 m o l e s

    27

    Formulas, Equations & Stoichiometry R e v i e w -Cut from Jan 2007 - Jan 2008 Exams

    1. W h i c h eq i i a l ion s h o w s conser^'ahoIl o f a toms?

    ( D l - b + O , ^ 1-1,0 ( 2 ) H , + O2 ^ 2 H2O ( 3 ) 2 H , + O2 2 H , 0 ( 4 ) 2 H2 + 2 O2 -> 2 H2O

    2. W h i c h substa j ice c a n be broken d o w n by a chemica l change?

    ( 1 ) an t imony ( 3 ) hexane ( 2 ) ca rbon ( 4 ) su l fu r

    3. What is the g ram f o r m u l a mass o f C a 3 ( P O j ) 2 ? (1) 248 g/mol ( 3 ) 279 g/mol ( 2 ) 263 g/niol ( 4 ) 3 I O g / m o I

    4. In w h i c h compound is the ratio o f metal ions to nonmeta l ions 1 to 2^

    (1) c a l c i u m b romide ( 2 ) c a l c i u m o x i d e ( 3 ) c a l c i u m phosphide ( 4 ) c a l c i u m su l f i de

    5. G i v e n the ba lanced equat ion represent ing a react ion:

    2 C O ( g ) + 0 , ( g ) ^ 2 C O , ( g ) What is the mo le rat io o f C C K g ) to C O i C g ) in this reac t ion? (1) 1:1 ( 3 ) 2 : 1 ( 2 ) 1:2 ( 4 ) 3 : 2

    6. G i v e n the ba lanced equat ion represent ing a react ion:

    H* (aq) + O l - r i a q ) ^ 1-1,0(0 + 55 ,8 kJ In this react ion there is conserva t ion o f { 1 ) m a s s , on l y ( 2 ) mass and charge , on l y ( 3 ) mass and energy , o n l y ( 4 ) m a s s , charge , and ene rgy

    7. W h i c h po l y a tom i c ion conta ins the greatest number o f o x y g e n a to ins?

    ( 1 ) acetone ( 3 ) hyd rox ide ( 2 ) ca rbonate ( 4 ) perox ide

    8. W h i c h fo rmu la represents an ion ic c o m p o u n d ?

    (1) H2 ( 3 ) C H , O H ( 2 ) C H j ( 4 ) N H j C l

    9. Wha t is the total number o f d i f fe rent e lements present in N H j N O , ?

    (1) 7 ( 3 ) 3 ( 2 ) 9 ( 4 ) 4

    10. W h i c h f o rmu la represents lead (11) chromate?

    (1) PbCrO . , ( 3 ) P b : C r O j ( 2 ) P b ( C i 0 4 ) , ( 4 ) P b , ( C r 0 4 ) 3

    11. W h i c h part ic le d i a g i a m lepresents a samp le o f one c o m p o u n d , on l y ?

    K e y

    O = a ' o m o f o n e e l e m e n t

    = a t o m o f a d i f f e r e n t e l e m e n t

    ( 1 ) ( 3 )

    (2) ( 4 )

    28

  • 12. A n atom in the ground slate conta ins a total o f 5 e lectrons, 5 protons, and 5 neutrons. W h i c h L e w i s electron-dot d iagram represents this a tom' '

    X ' X * : x : (1) (2) (3) (4)

    13. G i v e n the balanced equat ion represent ing the react ion between propane and o x y g e n :

    C j H g + 5 0 : -> 3 C O : - 4 H : 0 A c c o r d i n g to this equat ion , w h i c h ratio o f o x y g e n to propane is cor rec t ?

    5 grams O,, 10 jjrmns O, 1 gram C.Hj,

    5 moles O,, ! mole G.,Hs

    ( 3 )

    (-1)

    1J grams Cjll^

    10 moles O., I ! moles G.Hg

    14. W h i c h substance can be decomposed by chemica l means?

    ( 1 ) tungsten (3) k rypton ( 2 ) an t imony ( 4 ) methane

    15. G i v e n the balanced equat ion represent ing a react ion:

    4 N H , + 5 0 , -> 4 N 0 + 6H2O Wha t is the minininni number o f mo les o f O2 that are needed to comple te l y react w i th 16 mo les o f Nl-h? ( 1 ) 1 6 m o l ( 3 ) 6 4 m o l ( 2 ) 20 , mol ( 4 ) 80. mo l

    16. E l e m e n t -Vreacts w i th iron to form two di f ferent compounds w i t h the fo rmu las FeA" and Fe iA ' j . T o w h i c h group on the Pe r iod i c T a b l e does e lement ,\ 'belong? ( 1 ) G r o u p 8 ( 3 ) G r o u p 13 ( 2 ) G r o u p 2 ( 4 ) G r o u p 16

    17. T h e molar mass o f Ba (OH ) 2 is ( 1 ) 154.3 g ( 3 ) 171.3 g ( 2 ) 155.3 g ( 4 ) 308 . 6 g

    18. G i v e n the ba lanced equat ion represent ing a react ion:

    1 l2SOj(aq) + 2 K O H ( a q ) -> K 2 S 0 4 ( a q ) + IHiCKI) W h i c h type o f react ion is represented by this equat ion? ( 1 ) decompos i t ion ( 2 ) neutra l izat ion ( 3 ) s ingle replacement ( 4 ) synthes is

    19. A hydrated compound conta ins water mo lecu l es w i t h i n i ts c rys ta l s i m c l u r e T h e percent compos i t ion by mass o f water i j i the hydrated compound C a S O j ' 2 H 2 0 has an accepted va lue o f 2 0 . 9 % , A student d id an exper iment and dete rmined that the percent compos i t i on by mass o f w a t e r in C a S O j * 2 H 2 0 was 2 1 . 4 % .

    Ca l cu l a t e the percent e r ro r o f the student 's expe i imen ta l result . Y o u r res|X)nse must inc lude hoih a correct numer i ca l setup and the ca lcu la ted result . [ 2 ]

    20 . Wr i t e the emp i r i c a l f o m i u l a for the compound CgHig. [ 1 ]

    2 9

    B a s e y o u r a n s w e r s to q u e s t i o n s 21 t h r o u g h 2 3 o n the i n f o r m a t i o n b e l o w .

    S o m e dry c h e m i c a l s can be used to put out forest f i res . One o f these chem i ca l s is N a H C O i . W h e n N a H C O i ( s ) is heated, one o f the products i s C 0 2 ( g ) , as s h o w n in the ba lanced equat ion be low.

    2 N a H C O . , ( s ) + heat -> N a j C O j l s ) + H : 0 ( g ) + C 0 2 ( g )

    2 1 , S h o w a correct numer i ca l setup for ca l cu l a t i ng the percent compos i t i on by mass