A significant figure is defined as :

1.	The total number of digits in a number, including the last digit that represents the uncertainty of the result.
2.	The total number of digits in a number, excluding the last digit, which represents the uncertainty of the result.
3.	The total number of digits in a number including the last digit that represents the certainty of the result.
4.	The total number of last digits that represents the uncertainty of the result.

The chloroform contamination level in water is 15 ppm (by mass of chloroform). The molality of chloroform in the water sample would be:

1. 3.25 × 10^-4   

2. 1.5 × 10^-3 

3.  7.5 × 10^-3    

4. 1.25 × 10^-4  

If the speed of light is 3.0 × 10⁸ m s^–1, then the distance covered by light in 2.00 nanoseconds will be -

1. 0.500 m

2. 0.600 m

3. 0.700 m

4. 0.800 m

In a reaction A + B₂ → AB_2, 
A will act as a limiting reagent if :

 
Choose the correct option:

If 10 volumes of H₂ gas react with 5 volumes of O₂ gas, the volumes of water vapor produced would be:

1. 9

2. 8

3. 10

4. 11

15.15 pm in the basic unit will be 

1. 1.515 × 10^–12 m

2. 2.57 × 10^–11 m

3. 2.87 × 10^–11 m

4. 1.515 × 10^–11 m

Which will have the largest number of atoms among the following?

What would be the molarity of a solution of ethanol in water if the mole fraction of ethanol is 0.040?
(assume the density of water to be 1)
1. 3.143 M

2. 2.314 M

3. 2.413 M

4. 2.141 M

The mass of one ¹²C atom in g is:

1. 1.393 x 10^-23

2. 1.993 x 10^-23

3. 1.773 x 10^-23

4. 1.593 x 10^-23

The number of significant figures present in the answer of the following calculations [(i), (ii), (iii)]  are respectively -