How hydrogen is prepared in the laboratory?
How hydrogen is prepared in the laboratory?
Laboratory preparation of hydrogen
In the laboratory, hydrogen is prepared by reaction of dilute hydrochloric acid on granulated zinc.
Granulated zinc is the zinc-containing copper as an impurity. The presence of copper help speeds up the rate of chemical reaction which is why granulated zinc is preferred over pure zinc.
Procedure: place a few pieces of granulated zinc in a round bottom flask. fix a rubber cork with the two holes in the mouth of the flask. Pass a thistle funnel through one hole and the delivery tube through the other hole. Connect the other end of the delivery tube to a beehive shelf placed in a trough containing water. Pour dilute hydrochloric acid (HCl) down the thistle funnel until it covers zinc pieces. The granulated zinc piece does increase react with dilute hydrochloric acid producing zinc chloride and hydrogen gas.
Observation: As soon as you pour hydrochloric acid you will observe a brisk effervescence of the gas at the far end of the delivery tube. allow the first few bubbles of the gas to escape because it is mixed with air inside the flask. Now collect the gas by the downward displacement of water. for this, invert the gas jar completely filled with water over the beehive shelf. hydrogen displaces the water and is collected in the gas jar since it is almost insoluble in water and lighter than water. this method of collecting a gas is known as downward displacement of water. place a greased glass disc over the gas jar and remove it from the trough. hydrogen gas is collected by downward displacement of water.
The equation of the chemical reaction that takes place is as follows
Zinc + Dilute hydrochloric acid Zinc Chloride + Hydrogen gas
Precaution to be taken
- Do not collect the first few bubbles of the gas as they may contain air in it.
- Avoid keeping any type of flame near the Apparatus as hydrogen is highly inflammable gas
Laboratory preparation of hydrogen
In the laboratory, hydrogen is prepared by reaction of dilute hydrochloric acid on granulated zinc.
Granulated zinc is the zinc-containing copper as an impurity. The presence of copper help speeds up the rate of chemical reaction which is why granulated zinc is preferred over pure zinc.
Procedure: place a few pieces of granulated zinc in a round bottom flask. fix a rubber cork with the two holes in the mouth of the flask. Pass a thistle funnel through one hole and the delivery tube through the other hole. Connect the other end of the delivery tube to a beehive shelf placed in a trough containing water. Pour dilute hydrochloric acid (HCl) down the thistle funnel until it covers zinc pieces. The granulated zinc piece does increase react with dilute hydrochloric acid producing zinc chloride and hydrogen gas.
Observation: As soon as you pour hydrochloric acid you will observe a brisk effervescence of the gas at the far end of the delivery tube. allow the first few bubbles of the gas to escape because it is mixed with air inside the flask. Now collect the gas by the downward displacement of water. for this, invert the gas jar completely filled with water over the beehive shelf. hydrogen displaces the water and is collected in the gas jar since it is almost insoluble in water and lighter than water. this method of collecting a gas is known as downward displacement of water. place a greased glass disc over the gas jar and remove it from the trough. hydrogen gas is collected by downward displacement of water.
The equation of the chemical reaction that takes place is as follows
Zinc + Dilute hydrochloric acid Zinc Chloride + Hydrogen gas
Precaution to be taken
- Do not collect the first few bubbles of the gas as they may contain air in it.
- Avoid keeping any type of flame near the Apparatus as hydrogen is highly inflammable gas
