71. Artificial rain is caused by spraying

1. 1. Neutral charged colloidal dust over a cloud

   
   
   

   2. Similar charged colloidal dust over a cloud

   
   
   

   3. Both (a) and (b)

   
   
   

   4. Opposite charged colloidal dust over a cloud

   
   
   

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   NA

   Correct Option: D

   NA

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72. Sulphur sol contains

1. 1. discrete sulphur atoms

   
   
   

   2. discrete sulphur molecules

   
   
   

   3. large aggregates of sulphur molecules

   
   
   

   4. water disperesed in solid sulphur

   
   
   

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   NA

   Correct Option: C

   NA

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73. Gold number is the index for

1. 1. Protective colloid

   
   
   

   2. Metallic gold

   
   
   

   3. Troplated gold

   
   
   

   4. Purity of gold

   
   
   

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   NA

   Correct Option: A

   NA

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74. Whipped cream is an example of

1. 1. Liquid-gas

   
   
   

   2. Liquid-liquid

   
   
   

   3. Liquid-solid

   
   
   

   4. Solid-liquid

   
   
   

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   NA

   Correct Option: A

   NA

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75. Which of the following is not a colloid ?

1. 1. Chlorophyll

   
   
   

   2. Smoke

   
   
   

   3. Ruby glass

   
   
   

   4. Milk

   
   
   

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   NA

   Correct Option: A

   NA

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