Saturday 13 April 2013

JAWAPAN / SCHEM MODULE CHEMISTRY WAJA-CHAPTER 1-RATE OF REACTION


ANSWER
Activity

1
speed , product
reactants , products
2
1. S              2. S               3. F             4. S             5. F
6. F              7. S               8. S             9. S           10. F
3
decrease ,     increase,       increase,           forming

Eq 1 :          CaCO3  +  2HCl  →  CaCl2  +  CO2  +  H2O
Changes : - decrease in the mass of CaCO3
- increase in volume of CO2 released

Eq 2 :      Na2S2O3  +  H2SO4  →  Na2SO4  +  SO2  +  S  +  H2O
Change : time taken for the yellow precipitate of sulphur formed

Eq 3 :      2H2O2  →  2H2O  +  O2
Change : increase in the volume of oxygen gas
4
4A
2(a)  V4      ;    V2     ;      V3  - V2  ;  60  ;  V3  - V2 
        240         120                                      60
2(c)  V2  - V1
            160 - 30 

4B
1 Plot a graph


2 (i)  Average rate of reaction  ,   V    =    86    =  28.67 cm3min-1
     in the first 3 min                    t            3
(ii)         V  =  V3 – V2  =  86 – 70    =  16
               t   =    t3 – t2      =  3.0 – 2.0  =  1.0  

               Average rate of reaction    ,    V   =  16   =   16  cm3min-1
                             In the third min          t       1.0

(iii)       V  =  total volume of gas collected at 4.0 min (95 cm3)
             t  =  time taken for the reaction to be complete =  4.0 min
            Overall average rate of reaction , =  V   =  95   =   23.75  cm3min-1
                                                                      t        4.0

(iv)        Show a tangent  at the 1 min of the graph
             The instantaneous rate of reaction  at 1 min
             =  gradient of the curve at 1 min
             =  Y2 – Y1          =   70 – 30    =  40  =  26.67  cm3min-1
                 X2 – X            1.55 – 0.5      1.5
5
1
(a)  (i)      Average rate of reaction in the first 10 sec
=   20     =  2   cm3 s-1
                      10
(ii)           Average rate of reaction in the first 30 sec
=    46     =  1.53    cm3 s-1
                       30
(iii)          Overall average rate of reaction
=    50     =   1.25     cm3 s-1
                  40


(b) The rate of reaction decrease with time.
(c)  This is because the concentration of
      hydrochloric acid, HCl decreases. When there is no more hydrochloric acid,
      HCl remaining, the reaction is complete and the rate of reaction is zero.

2
(a) the first 60 seconds     =   29  -  17    =  12        =    0.4  cm3s-1                                                        
                                               60 -  30         30                                                                                                                                                                                                                         
(b) the overall reaction        =     36        =   0.3   cm3s-1
                                                  120

3
0.0036 g min-1
6
(a)
(b)
(c)
(d)
(e)
The size of solid reactant/ Total surface area of solid reactant
Temperature
Concentration of reactant
Presence of catalyst
Pressure of gaseous reactant
     7
1
2
3
4
5
6
7
8
Temperature
X

Concentration
Size of reactant
X

Presence of catalyst
Pressure
X

8
(i)
CaCO3  +  2HCl  →  CaCl2  +  CO2  +  H2O
  • Steeper
  • Higher
  • Larger/bigger, higher

(ii)
Na2S2O3  +  2HCl → 2NaCl + S  + H2O  +  SO2.
  • Shorter
  • The rate of reaction
  • Higher ,  higher

(iii)
2H2O2  →  O2  + 2H2O
  • Steeper
  • Higher
  • Increase

(iv)
Na2S2O3  +  2HCl → 2NaCl + S  + H2O  +  SO2.
  • Shorter
  • The rate of reaction
  • Higher , higher
9
1

low (-30 – 10oC) ,  active ,  toxic ,  lower.
high (25 – 40 oC)  ,  more  ,  lot of ,  higher
2
smaller ,   smaller  ,  total surface area,   higher
3
(i) ammonia ,  N2  +  3H2  ↔  2NH3 ,   450 – 550oC ,  200 – 400 atm,  iron
(ii) contact ,  2SO2  +  O2  ↔  2SO3  ,  450 oC  ,  1 atm  ,  vanadium(V) oxide
10
1
(i) collision between  particles
(ii) effective collisions
(iii) activation energy
2
(i) collide
(ii) product
(iii) effective ,  activation energy
3
Minimum

4
Reactant


11


Ea : Activation energy
Ea’ : Activation energy in the presence of catalyts
12



(i)
total surface arealarger   ,  increases  ,   increase  ,  higher 
(ii)
lower , incrases , higher
(iii)
kinetic energy  ,  faster   ,  increasemore  ,  increasing of   , higher  
(iv)
increase  , number  ,  increases  , increases , higher 
13





















1









2












Volume of hydrogen gas /cm3
 









Volume of hydrogen gas /cm3
 





                                                                                   

Time (s)
 
55
 
 



   14
1






2
(a) Zn  +  H2SO4  →  ZnSO4  +  H2
(b) Overall average rate of reaction  =  210     =  ……………. cms-1
                                                              150
(c) (i)
     (ii) [Draw a tangent at 80 s] [Rate of reaction  =  gradient of the tangent]
(d) The decreasing of the mass of zinc used.

(i) higher ,  higher  ,   higher ,  collision  ,  increases  ,  effective  ,  higher.
(ii) higher ,  bigger.larger ,  collision,    increases , effective ,  higher.

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