hydrogen

1. hydrogen NAME :

2. INTRODUCTIONRobert Boyle prepared hydrogen gas in 1672. However, he was unable to establish that it was an element. The credit for the discovery of hydrogen goes to Henry Cavendish_He prepared hydrogen by the action of hydrochloric acid on iron metal in 1766. He also established that it is an element. He proved that when hydrogen is burnt in air, it forms water. In Greek language water maker is called hydrogen. Thus, Cavendish named the gas hydrogen.OCCURRENCEHydrogen does not exist in free state in atmosphere. However, in sun and stars, free hydrogen is

3. the chief constituent.In combined state, hydrogen occurs as water. Every 9 g of water contains 1 g of hydrogen. Hydrogen is a vital constituent of the compounds (carbohydrates, fats, proteins, etc.), which form the bodies of animals and plants. It is present in large amount in mineral products, such as petroleum, natural gas, coal, etc. Hydrogen is an essential constituent of all acids and alkalis.

4. USES OF HYDROGEN GAS • . These are useful in forecasting weather.However hydrogen filled balloons have a disadvantage, i.e., they can catch fire in case of lightning. These days the weather forecasting balloons are filled with equal volumes of hydrogen and helium gases.These balloons do not cause accidental fires.Urea- NH, CONH23. For the manufacture of chemicals AJHydrogen gas is extensively used in the manufacture of ammonia gas and hydrochloric acid gas. Ammonia gas is further used in the manufacture of fertilisers like ammonium sulphate and urea. Similarly, hydrochloric acid is also used in a number of industrial processes.

5. 4. For hydrogenation of vegetable oilsVegetable oils do not solidify at room temperature. They are complex compounds of carbon, hydrogen and oxygen, but are deficient in hydrogen.These oils are decolourised and deodorised. They are then mixed with finely divided (finely powdered) nickel metal and are heated to 200°C. Hydrogen gas is passed through the mixture at a pressure of 5 atmospheres. The gas reacts with oils and the product, so formed, tends to solidify at room temperature. The nickel metal is filtered out and product is marketed as vanaspati ghee. The nickel metal acts as catalyst.

6. USES OF HYDROGEN GASTYENVOWOZIF • welding and cutting purposesA flame of hydrogen and oxygen has a temperature of around 2800°C.This flame is called oxy-hydrogen flame and is used for cutting and welding purposes.9/4④2. Fer meteorological purposesHydrogen is the lightest element. Hydrogen filled balloons are sent up along with meteorological instruments to record temperature, wind speed, air pressure, etc

7. CHEMICAL PROPERTIES OF HYDROGEN GAS1. • Combustibility : Hydrogen is a combustible gas, but it does not support combustion.Pure hydrogen burns silently in air (or oxygen) with a pale-blue flame.However, a mixture of hydrogen and air lor oxygen explodes with a pop sound, because of spontaneous combustion.Flame of hydrogen gas

8. Hydrogen is a combustible gasWARNINGXrWithsmallquantitiesof mixture of hydrogen gas and air, the explosion is not dangerous.However,whileworking with large volumes of the mixture, the explosion could be very serious, specially if the container is made of glass. It will almost explode like a bomb causing serious injuries.It is for the same reason that no flame should be brought near hydrogen gas apparatus while preparing the Bas in laboratory.ExperimentTake a gas jar filled with hydrogen and cover it with a glass disc.Over this jar invert another jar containing air as shown in

9. Remove the glass disc so that a mixture of hydrogen and air is formed as shown in Now ignite a long wooden splinter such that its one end catches fire. Introduce the burning splinter in the mixture of hydrogen and air. It is observed :(i) The flame of the splinter goes off.(ii) The gas explodes with a sharp pop sound and burns near the mouth of cylinder with a pale-blue flame as shown in

10. The above fact is used for testing hydrogen gas.2. Action with litmus: Hydrogen gas is neutral towards litmus. It means it neither turns moist blue litmus paper red nor red litmus paper

11. Ondlecirolsis of ecidulated water Iwo volumes of oiygenand one volume of tydroeare formed.4. EIn sulphate is used as catalyst during laboratory preparation of hydrogen gas.5. Calcium reacts with cold water and forms calcium hydroxide and hydrogen gas.E. Tick (V) the most appropriate answer.1. The credit of discovery of hydrogen goes to:ได้ Herry Cavendish•(d) Francis Bacon(a) Lavoisier(b) Robert Boyle2. In free state hydrogen gas is present in :(c) petroleum gas(d) coal gas(a) natural gastol stars3. The metal which does not react with dilute sulphuric acid is :(el copper(d) iron(a) aluminium(b) zinc4. The substance|s) which contain hydrogen in combined state

12. PHYSICAL PROPERTIES OF HYDROGEN GAS • MQAEDLOP821. Colour, odour and taste: Pure hydrogen is (i) colourless gas,(i) tasteless gas, and iii) odourless gas.2. Vapour density : Hydrogen is the lightest element. Its vapour density is 1, as compared to air's being

13. 5HydrogenPlatinum-electrodes • XAs - Fig. 7.1 : Electrolysis of waterNOTESatalyst is a substance which speeds up rate of chemical reaction but self does not undergo a remical change.98BY THE ELECTROLYSIS OF WATERWhen electric current is passed through acidulated water water. containing sulphuric acid), it splits into hydrogen and oxygen.2H,0 (acidulated)Electric , current2H2+HydrogenWaterOxygen

14. shows a voltameter fitted with platinum electrodes. Acidulated water is poured in voltameter.Test tube filled with acidulated water is inverted overOxygeneach electrode. When the current is passed from a battery, it decomposes water into hydrogen and oxy-gen. The hydrogen is collected at negative electrode and oxygen at positive electrode. The ratio by volumes- Acidulated waterof

15. H2: 02 = 2: 1. Xhs - 5Electrolysis and Terms related to it.Electrolysis: It is a process in which electric current is passed through an aqueous solution or a molten (fused) state of a compound, resulting in a chemical change.Thus, during electrolysis, a chemical change is brought about by electric energy.Electrolyte: It is an aqueous solution or molten state of a compound which conducts electric current through it, because it has free mobile ions.Electrodes:

16. Two conducting poles placed in an electrolyte such that current enters and leaves through them, are called electrodes. Generally, they are made up of metals or graphite. These two electrodes are called anode and cathode.Anode: The electrode connected to the positive terminal of battery is called anode.Cathode: The electrode connected to the negative terminal of the battery is called cathode.

17. Two conducting poles placed in an electrolyte such that current enters and leaves through them, are called electrodes. Generally, they are made up of metals or graphite. These two electrodes are called anode and cathode.Anode: The electrode connected to the positive terminal of battery is called anode.Cathode: The electrode connected to the negative terminal of the battery is called cathode.LABORATORY PREPARATION OF HYDROGENZJIFXPVLOKIn laboratory, hydrogen gas is prepared by treating granulated zinc (granulated means with roughened surface) with dilute sulphuricacid.Following reaction takes place.Zn +H,SO, (dit.)+ZincSulphuricacidZincsulphateH,(g)HydrogenExperimentTake a clean conical flask and place about 5 g of granulated zinc in it. In the mouth of flask fix a two-holed air tight stopper. ThroughEXID.

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