MATERIAL REQUIRED
Wolff Bottle, thistle funnel and delivery tube fitted with cork, pneumatic trough, beehive shelf, gas jar, Dilute Sulphuric acid or Hydrochloric acid
THEORY
Hydrogen is a reactive element and thus does not occur much in the free state. It is found in volcanic gases and natural gases in trace amount but it occurs abundantly in a combined state. In the combined form, it is an important constituent of water, acid, alkali and many organic compounds of vegetables and animal products. The chief source of hydrogen is water in which its amount is double in comparison to oxygen.
The laboratory preparation of hydrogen gas usually involves the action of dilute sulphuric acid or dilute hydrochloric acid on zinc granules. Granulated zinc is ideal for the preparation of hydrogen gas in chemical laboratories because it usually contains a small amount of copper, which has the ability to act as a catalyst for the associated chemical reaction and, therefore, increases the rate of the chemical reaction without actually participating in it. It is exothermic reaction which generate more heat.
General Format: Metal + Dilute Acid → Salt of Metal & Acid + Hydrogen
With Hydrochloric Acid: Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
With Sulphuric Acid: Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)
PROCEDURE
- Take a clean dry woulff bottle with zinc granulate.
- Fit cork with thistle funnel and delivery tube.
- Cover another end of delivery tube by beehive shelf in water trough.
- Filled water trough with two third of water.
- Take a gas jar and filled with water and cover by glass plate without producing bubble at top.
- Pour about 30 ml of dilute sulphuric acid or hydrochloric acid through thistle funnel. Thistle funnel must be dipped in dilute acid.
- Wait about 1 minutes to escape air bubble from delivery tube for complete removal of air from conical flask.
- Then invert gas jar with glass plate over the beehive shelf under water in water trough.
- Finally remove glass plate.
- Then hydrogen gas is collected in gas jar by downward displacement of water.
OBSERVATION
- Hydrogen gas is collected by downward displacement of water.
- When burning 🔥 wood piece is inserted it extinguished and hydrogen is burn with pop sound.
- Wulff bottle is heated during reaction
RESULT
- Hydrogen gas extinguish burring material.
- It is lighter than air
- It burn with oxygen by producing pop sound
CONCLUSION
Hydrogen gas is prepared in laboratory by displacing hydrogen of acid by zinc metal.
PRECAUTION
- Impure zinc should be used instead of pure.
- Concentrated sulphuric acid should not be used
- The end of thistle funnel must be under the acid in Woulfe’s bottle and delivery tube must be above the acid .
- The apparatus should be clean and made airtight.
- The bee-hive shelf should be under the water level in the pneumatic trough.
- The experiment should be conducted far away from fire.
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