Which property makes hydrogen the lightest element?

It has one proton and one electron only

Explain the Bosch Process for industrial hydrogen production.

The Bosch Process involves three steps: 1. Water Gas Production: Red hot carbon reacts with steam at $\approx 1000^{\circ}C$ to form water gas ($CO + H_2$). 2. Conversion of $CO$ to $CO_2$: Water gas is mixed with more steam and passed over $Fe_2O_3/Cr_2O_3$ catalyst at $450^{\circ}C$ to convert $CO$ to $CO_2$, yielding more $H_2$. 3. Removal of $CO_2$: The mixture is passed through water under 30 atm pressure, where $CO_2$ dissolves, leaving pure $H_2$.

Describe the electrolysis of water for hydrogen preparation.

Electrolysis of water involves passing an electric current through acidified water ($H_2O$ with dilute $H_2SO_4$). Hydrogen gas ($H_2$) is collected at the cathode (negative terminal), and oxygen gas ($O_2$) is collected at the anode (positive terminal). The reaction is $2H_2O(l) \xrightarrow{\text{electric current}} 2H_2(g) + O_2(g)$.

Hydrogen Science PW ICSE Complete

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Video Summary

Hydrogen: Properties, Preparation, and Uses

Hydrogen is the simplest and lightest element, with an atomic structure consisting of one proton and one electron, and typically no neutron. It is the first element in the periodic table and is the most abundant element in the universe, making up approximately 90% of all matter. On Earth, hydrogen is rarely found in its free state and is mostly present in combined forms such as water, acids, bases, and organic substances.

Basic Characteristics and Occurrence

Hydrogen is unique due to its simplicity and abundance. Its atomic mass is approximately $1\,u$ , making it…

Hydrogen: Properties, Preparation, and Uses

Hydrogen is the simplest and lightest element, with an atomic structure consisting of one proton and one electron, and typically no neutron. It is the first element in the periodic table and is the most abundant element in the universe, making up approximately 90% of all matter. On Earth, hydrogen is rarely found in its free state and is mostly present in combined forms such as water, acids, bases, and organic substances.

Basic Characteristics and Occurrence

Hydrogen is unique due to its simplicity and abundance. Its atomic mass is approximately $1\,u$ , making it the lightest element. In the universe, hydrogen is found in large quantities, especially in stars and the sun, but on Earth, it is mostly found in compounds.

Atomic Structure: 1 proton, 1 electron, usually no neutron.
Atomic Mass: Approximately $1\,u$ .
Abundance: About 90% of the universe's matter contains hydrogen.
Occurrence on Earth: Rarely free; mainly in compounds like water, acids, bases, carbohydrates, proteins, and hydrocarbons.
Examples of Compounds: Methane ( $CH_4$ ), ethane ( $C_2H_6$ ), water ( $H_2O$ ).

Discovery of Hydrogen

The discovery of hydrogen involved several scientists and key experiments. Robert Boyle first observed the production of a gas by reacting iron filings with dilute acid in 1767, but did not identify it. Henry Cavendish later identified the gas as highly inflammable and called it "inflammable air," suggesting it was a new element. Finally, in 1781, Lavoisier named it "hydrogen," meaning "water former," as it forms water when burned.

Robert Boyle (1767): Observed gas from iron and dilute acid.
Henry Cavendish: Identified inflammable nature, called it "inflammable air."
Lavoisier (1781): Named it "hydrogen" (hydro = water, gen = producer).

Preparation of Hydrogen

Hydrogen can be prepared by several methods, mainly involving reactions with water, alkalis, acids, and by industrial processes. The reactivity of metals with water depends on the temperature and the metal used.

From Cold Water: Highly reactive metals like potassium, sodium, and calcium react with cold water to form their respective hydroxides and hydrogen gas.
- Potassium: $2K + 2H_2O \rightarrow 2KOH + H_2$
- Sodium: $2Na + 2H_2O \rightarrow 2NaOH + H_2$
- Calcium: $Ca + 2H_2O \rightarrow Ca(OH)_2 + H_2$
From Hot Water: Magnesium reacts with hot water to form magnesium hydroxide and hydrogen.
- $Mg + 2H_2O \rightarrow Mg(OH)_2 + H_2$
From Steam: Metals like aluminum, zinc, and iron react with steam to form oxides and hydrogen.
- Aluminum: $2Al + 3H_2O \rightarrow Al_2O_3 + 3H_2$
- Zinc: $Zn + H_2O \rightarrow ZnO + H_2$
- Iron: $3Fe + 4H_2O \rightarrow Fe_3O_4 + 4H_2$
By Action of Hot Alkalis: Aluminum, zinc, and lead react with hot alkalis (e.g., NaOH) to form complex salts and hydrogen.
- Aluminum: $2Al + 2NaOH + 2H_2O \rightarrow 2NaAlO_2 + 3H_2$
- Zinc: $Zn + 2NaOH \rightarrow Na_2ZnO_2 + H_2$
- Lead: $Pb + 2NaOH \rightarrow Na_2PbO_2 + H_2$
By Action of Dilute Acids: Moderately reactive metals like magnesium, zinc, and iron react with dilute acids (HCl or $H_2SO_4$ $H_{2} S O_{4}$ ) to produce hydrogen.
- $Zn + 2HCl \rightarrow ZnCl_2 + H_2$
- $Fe + 2HCl \rightarrow FeCl_2 + H_2$
- $Mg + H_2SO_4 \rightarrow MgSO_4 + H_2$
Electrolysis of Water: Passing electric current through acidified water (with dilute $H_2SO_4$ ) using platinum electrodes produces hydrogen at the cathode and oxygen at the anode.

Laboratory and Industrial Preparation

Hydrogen is prepared in the laboratory and industry using specific setups and processes.

Laboratory Preparation: Zinc granules react with dilute hydrochloric acid in a setup where the evolved hydrogen gas is collected over water by displacement.
- $Zn + 2HCl \rightarrow ZnCl_2 + H_2$
Industrial Preparation (Bosch Process):
1. Step 1: Steam is passed over red-hot coke (carbon) at about $1000^\circ C$ $100 0^{\circ} C$ to produce water gas (CO + $H_2$ $H_{2}$ ).
  - $C + H_2O \rightarrow CO + H_2$
2. Step 2: Water gas is further treated with steam at $450^\circ C$ $45 0^{\circ} C$ in the presence of iron oxide ( $Fe_2O_3$ $F e_{2} O_{3}$ ) catalyst and chromium oxide ( $Cr_2O_3$ $C r_{2} O_{3}$ ) promoter to convert CO to $CO_2$ $C O_{2}$ and produce more $H_2$ $H_{2}$ .
  - $CO + H_2O \rightarrow CO_2 + H_2$
3. Step 3: $CO_2$ is removed by dissolving in water under 30 atm pressure, leaving pure hydrogen.
4. Purification: $CO_2$ and CO can be further removed by passing the gas through KOH and ammoniacal $CuCl$ respectively.

Physical Properties of Hydrogen

Hydrogen is a colorless, odorless, tasteless, and non-poisonous gas. It is extremely light, being 20 times lighter than air, and has very poor solubility in water. It can be liquefied at very low temperatures and high pressures.

Color/Odor/Taste: None.
Toxicity: Non-poisonous.
Density: 20 times lighter than air.
Solubility: Poorly soluble in water.
Liquefaction: At $-240^\circ C$ and about 40 atm pressure.
Boiling Point: $-253^\circ C$ .
Melting Point: $-259^\circ C$ .
Flammability: Highly flammable; burns with a pale blue flame and produces a pop sound when ignited.

Chemical Properties of Hydrogen

Hydrogen reacts with various elements and compounds, often requiring specific conditions such as catalysts, temperature, or pressure.

With Chlorine: In sunlight, hydrogen reacts with chlorine to form hydrogen chloride gas. The reaction is slow in dim light and explosive in bright sunlight.
- $H_2 + Cl_2 \rightarrow 2HCl$
With Nitrogen (Haber Process): At $400^\circ C$ $40 0^{\circ} C$ and 200 atm pressure, in the presence of iron catalyst, hydrogen reacts with nitrogen to form ammonia.
- $N_2 + 3H_2 \rightarrow 2NH_3$
With Sulfur: With molten sulfur, hydrogen forms hydrogen sulfide gas ( $H_2S$ ).
With Carbon Dioxide: Hydrogen reacts with $CO_2$ to form methane ( $CH_4$ ), water, and energy.
With Carbon: Hydrogen reacts with carbon to form methane.
With Reactive Metals: Forms hydrides such as sodium hydride ( $NaH$ ) and calcium hydride ( $CaH_2$ ).

Oxidation, Reduction, and Redox Reactions

Oxidation involves the addition of oxygen or removal of hydrogen, while reduction involves the addition of hydrogen or removal of oxygen. Redox reactions are those in which both oxidation and reduction occur simultaneously.

Oxidation: Addition of oxygen or removal of hydrogen.
Reduction: Addition of hydrogen or removal of oxygen.
Oxidizing Agent: Substance causing oxidation.
Reducing Agent: Substance causing reduction.
Redox Reaction Example: In the reaction $CuO + H_2 \rightarrow Cu + H_2O$ , $CuO$ is reduced to $Cu$ (removal of oxygen), and $H_2$ is oxidized to $H_2O$ (addition of oxygen).

Other examples:
- $PbO + H_2 \rightarrow Pb + H_2O$
- $Fe_2O_3 + 3H_2 \rightarrow 2Fe + 3H_2O$
- $ZnO + H_2 \rightarrow Zn + H_2O$

Uses of Hydrogen

Hydrogen has several important uses in industry and daily life. It is used in the production of ammonia (for fertilizers), methanol, and other organic compounds. It is also used in hydrogenation of vegetable oils, as a reducing agent in metallurgy, in welding and cutting metals, and as a rocket fuel.

Production of Ammonia: Used in the Haber process for fertilizers.
Manufacture of Methanol and Organic Compounds: Key raw material.
Hydrogenation of Oils: Converts unsaturated oils to saturated fats (e.g., vanaspati ghee).
Reducing Agent: Used in metallurgy for extracting metals.
Welding and Cutting: Oxy-hydrogen flame (temperature approx. $2800^\circ C$ ).
Rocket Fuel: Liquid hydrogen is used due to its high energy and clean combustion (produces only water).
Clean Energy: Considered a future fuel as it produces water on burning and does not pollute.

Key Exam Takeaways

Understanding the preparation, properties, and uses of hydrogen is crucial. Focus on the methods of preparation (especially laboratory and industrial), physical and chemical properties, key reactions (with chlorine, nitrogen, sulfur, etc.), and the concepts of oxidation, reduction, and redox reactions. Remember the significance of the Bosch and Haber processes, and the practical applications of hydrogen in industry and as a clean fuel.

Quiz

20 Questions

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Question 1 of 20

Which of the following statements about the given
reaction are correct?
3Fe(s) + 4H₂O(g)→Fe₃O₄ (s) + 4H₂(g)
(i) Iron metal is getting oxidised
(ii) Water is getting reduced
(iii) Water is acting as reducing agent
(iv) Water is acting as oxidising agent

Flashcards

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Question01 / 05

What is Hydrogen?

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Answer01 / 05

Hydrogen is the simplest and lightest element, with an atomic structure of one electron and one proton, and no neutron. Its atomic mass is approximately 1 u. It is the first element in the periodic table and the most abundant element in the universe.