When water is electrolysed it breaks down into hydrogen and oxygen:
2h2o
2h₂ + o2
what mass of hydrogen is produced by the electrolysis of 6g of water?

0.67 g

Explanation:

Data given

water (H₂O) = 6 g

Mass of Hydrogen = ?

Electrolysis of water

                    2H₂O > 2H₂ + O₂

Solution:

In hydrolysis of water the water molecule splits in hydrogen and oxygen

                     2H₂O > 2H₂ + O₂

So,  we know from reaction that 2 mole of water molecule splits in 2 mole of hydrogen and 1 mole of oxygen

                     2H₂O > 2H₂ + O₂

                     2mol              2 mol

If we represent mol in grams

Then,

Molar mass of water (H₂O) = 2(1) + 16

Molar mass of water (H₂O) = 18 g/mol

                    2H₂O        > 2H₂ + O₂

             2 mol (18 g/mol)         2 mol (2 g/mol)

                      2H₂O  > 2H₂ + O₂

                        36 g              4 g

It is obvious from the reaction that 36 g of water give 4 g of hydrogen on electrolysis.

Then how many grams of hydrogen will produce if 6 grams of water electrolyzed

apply unity formula

                      36 g of H₂O ≅ 4 g of H₂

                       6 g of H₂O ≅ x g of H₂

By doing cross multiplication

                         g of H₂ = 4 x 6 / 36

                          g of H₂ = 0.67 g

0.67 g of hydrogen will produce if 6 grams of water is electrolyzed

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.