The illustration to the left represents a mixture of hydrogen ( light blue ) and iodine ( purple ) reacting to form a product. In the illustration: The product that forms is . The number of product molecules formed is . The limiting reagent is

1. Hydrogen Iodide

2. 6 molecules of Hydrogen Iodide

3. Iodine is the limiting reagent

Explanation:

The image of the illustration in the question has been attached:

1. The illustration represents a mixture of hydrogen ( light blue ) and iodine ( purple )

H₂ + I₂ ---> 2HI

This forms hydrogen iodide.

2. In the given illustration, 6 product molecules of Hydrogen Iodide. This is indicated in the box on the right side of the illustration.

3.  The limiting reagent is the reactant that determines how much of the products are made. It is the substance that is totally consumed when the chemical reaction is completed. In the box on the right side of the illustration, you will see that hydrogen which is indicated by blue is in excess. The limiting reagent is the one that is completely consumed which is the iodine.

a mercury barometer is a device that uses the physical properties of mercury in a tube to measure barometric pressure. mercury barometers are used for : -

1. measurement of atmospheric pressure  

2. determining the altitude of a place

3. weather forecasting

4. calibration and checking of aneroid barometers

5. application in fluid mechanics

6. measurement of pressure in aircrafts

7. surface weather analysis

8. preparation of barographs

9. usage in physical sciences like physics, astronomy & chemistry

10. preparation of aircraft altimeters

characteristics of mercury barometer : -

1.used to define and measure atmospheric pressure.

2.on the average at sea level the column of mercury rises to a height of about 760 mm.

3.this quantity is equal to 1 atmosphere.

4.it is also known as standard atmospheric pressure.

5.a barometer in which the weight of a column of mercury in a glass tube with a sealed top is balanced against that of the atmosphere pressing on an exposed cistern of mercury at the base of the mercury column, the height of the column varying with atmospheric pressure.

it means there are 3 atoms of oxygen