Chemistry and Electricity

Chemistry and Electricity βš—οΈβš‘

Electrochemistry πŸ”‹

Electrolysis πŸ’§

Electrolysis is the decomposition of an electrolyte by using an electric current. ⚑

Electrolytes πŸ’§

An electrolyte is a substance that conducts electricity in fused (molten) or solution form and decomposes as a result. ⚑

Examples of Electrolytes 🌟

Strong Electrolyte πŸ’ͺ

It is a substance that ionizes completely and produces many ions in solution that carry electric current rapidly. ⚑

Examples of Strong Electrolytes πŸ’ͺ

Weak Electrolyte 🌱

It is a substance that ionizes partially and conducts electric current slightly, leading to partial decomposition. 🌊

Examples of Weak Electrolytes 🌱

Non-Electrolyte 🚫

A non-electrolyte is a substance that does not conduct electricity in fused or solution form because it exists as molecules rather than ions. ❌

Examples of Non-Electrolytes 🚫

Conductors and Insulators πŸ”Œ

Conductor ⚑

A conductor is a solid that allows electricity to pass through without decomposing, e.g., all metals. πŸ”‹

Non-Conductor 🚫

Also known as an insulator, it is a solid that does not conduct electricity, e.g., plastics, wood, and glass. 🧱

Electrodes βš™οΈ

Anode πŸ”‹

The anode is a positively charged electrode connected to the positive terminal of the power supply. βž•

Cathode βž–

The cathode is a negatively charged electrode connected to the negative terminal of the power supply. βž–

Cations and Anions βš›οΈ

Cations πŸ”‹

Cations are positively charged ions. βž•

Cation Formula
Aluminium ion Al3+
Calcium ion Ca2+
Hydrogen ion H+
Magnesium ion Mg2+
Sodium ion Na+

Anions βš›οΈ

Anions are negatively charged ions. βž–

Anion Formula
Bromide ion Br-
Chloride ion Cl-
Hydroxide ion OH-
Iodate ion IO-
Sulphate ion SO42-

The Ionic Theory βš›οΈ

The ionic theory states that electrolytes contain ions, and when no current is passing, ions move randomly in the solution. If an electric circuit is closed, the cathode becomes negatively charged and attracts cations, while the anode becomes positively charged and attracts anions. ⚑

Selective Order of Discharge of Ions ⚑

The discharge of ions in an electrolyte depends on:

Position of Ions in the Electrochemical Series πŸ“Š

Ions are arranged in decreasing order of stability in the electrochemical series. Less stable ions are discharged before more stable ions, and positive ions are discharged at the cathode while negative ions are discharged at the anode. ⚑

For example, H+ is discharged at the cathode in preference to Na+, and OH- is discharged at the anode in preference to Cl-.

Concentration of Ions in Aqueous Solution πŸ’§

For anions, concentration plays a role in determining which ion is discharged. In cases like concentrated sodium chloride, Cl- ions are discharged in preference to OH- ions due to the higher concentration. πŸ’§

Nature of Electrodes βš™οΈ

Inert electrodes such as platinum or graphite do not affect the selective discharge of ions, but active electrodes like copper influence which ions are discharged based on their reactivity. ⚑

Electrolysis of Lead (II) Bromide βš—οΈ

During the electrolysis of lead (II) bromide:

Electrolysis of Acidified Water πŸ’§

Pure water is a weak electrolyte, but the addition of an acid (like HCl or H2SO4) makes it conductive. In acidified water:

Electrolysis of Sodium Chloride (Brine) πŸ§‚

In the electrolysis of brine (concentrated sodium chloride solution):

The remaining sodium ions and hydroxide ions combine to form sodium hydroxide, making the solution alkaline. 🌊

Industrial Applications of Electrolysis 🏭

Electrolysis has several important applications in industry:

Faraday’s Laws of Electrolysis βš–οΈ

Faraday’s First Law βš–οΈ

The first law states that the mass of a substance produced at an electrode is directly proportional to the quantity of electricity passed through the electrolyte. ⚑

m ∝ Q, where Q = It (with I being current and t time). ⏳

Faraday’s Second Law βš–οΈ

The second law states that when the same quantity of electricity is passed through different electrolytes, the number of moles of elements deposited is inversely proportional to the charges on their ions. βš–οΈ

1 Faraday (F) = 1 mole of electrons = 96500 Coulombs. ⚑

Alloys βš™οΈ

An alloy is a mixture of two or more metals, or a metal with a non-metal, to create a substance with enhanced properties like strength and corrosion resistance. πŸ’ͺ

Alloy Composition Properties Uses
Brass Copper, Zinc Harder than copper, resistant to corrosion Used in musical instruments 🎢
Bronze Copper, Tin Harder than copper Used in medals and statues πŸ…
Stainless Steel Iron, Chromium, Nickel Does not rust Used in cutlery and surgical instruments 🍴
Solder Tin, Lead Low melting point Used for soldering πŸ”§

Metals and Their Properties βš™οΈ

Metals generally share several physical properties:

The Reactivity Series πŸ“Š

The reactivity series ranks metals from most to least reactive, determining their behavior in reactions with water, steam, and acids. Metals high in the series lose electrons more easily, making them more electropositive, while metals lower in the series are less reactive. ⚑

Metal Symbol
Potassium K
Sodium Na
Calcium Ca
Magnesium Mg
Aluminium Al
Zinc Zn
Iron Fe
Lead Pb
Hydrogen H
Copper Cu
Mercury Hg
Silver Ag
Gold Au

Reaction of Metals with Water or Steam πŸ’§

Metal Symbol Reaction with Cold Water πŸ’§ Reaction with Steam πŸ’¨
Potassium K Reacts very violently to produce potassium hydroxide and hydrogen gas πŸ’₯ β€”
Sodium Na Reacts violently to produce sodium hydroxide and hydrogen gas πŸ’₯ β€”
Calcium Ca Reacts less violently to produce calcium hydroxide and hydrogen gas πŸ’§ β€”
Magnesium Mg Reacts very slowly with cold water but violently with steam πŸ’§ Mg(s) + H2O(g) β†’ MgO(s) + H2(g)
Iron Fe β€” Fe(s) + H2O(g) β†’ FeO(s) + H2(g)
Copper Cu No reaction 🚫 No reaction 🚫

Reaction of Metals with Dilute Hydrochloric Acid πŸ’§

Metal Reaction
Potassium Explosive reaction: K(s) + HCl(aq) β†’ KCl(aq) + H2(g) πŸ’₯
Calcium Reacts vigorously to produce calcium chloride and hydrogen gas: Ca(s) + 2HCl(aq) β†’ CaCl2(aq) + H2(g) πŸ’₯
Magnesium Reacts rapidly to produce magnesium chloride and hydrogen gas: Mg(s) + 2HCl(aq) β†’ MgCl2(aq) + H2(g) πŸ’¨
Iron Reacts slowly to produce iron (II) chloride and hydrogen gas: Fe(s) + 2HCl(aq) β†’ FeCl2(aq) + H2(g) πŸ’¨
Lead Slow reaction, only with concentrated acid: Pb(s) + 2HCl(aq) β†’ PbCl2(aq) + H2(g) πŸ’¨
Copper No reaction 🚫

Recycling of Metals ♻️

Metals are finite resources, and recycling helps conserve these resources and reduce environmental impacts associated with mining. 🌍

Extraction of Metals βš’οΈ

Metals are extracted from ores based on their reactivity:

Examples of Extraction Methods βš’οΈ

Metal Symbol Extraction Method
Potassium K Electrolysis ⚑
Iron Fe Reduction with carbon in blast furnace πŸ”₯
Copper Cu Thermal decomposition πŸ”₯

Industrial Applications of Extracted Metals 🏭

Metals extracted through various methods are utilized in multiple industries:

Effects of Heat on Compounds πŸ”₯

Effects of Heat on Carbonates πŸ”₯

Carbonates of Group I elements (e.g., potassium, sodium) are very stable and do not decompose easily when heated. Carbonates of Group II elements (e.g., calcium, magnesium) and some transition metals decompose to form oxides and carbon dioxide:

Effects of Heat on Nitrates πŸ”₯

Nitrates also decompose when heated, with different products depending on the element:

Aluminium πŸͺ¨

Abundance: Aluminium is the most abundant metal in the Earth’s crust. It is extracted from bauxite (aluminium oxide) via electrolysis. βš’οΈ

Extraction of Aluminium βš’οΈ

Aluminium extraction requires bauxite dissolved in cryolite to reduce melting temperature. The process occurs in an electrolytic cell:

The carbon anodes react with oxygen to form CO2, so they are regularly replaced. πŸ”„

Uses of Aluminium πŸͺ¨

Copper πŸͺ¨

Ores: Common ores include malachite (CuCO3) and copper pyrites (Cu2S). πŸͺ¨

Extraction of Copper βš’οΈ

Copper is extracted by roasting copper (I) sulphide in controlled air:

Cu2S + O2 β†’ 2Cu + SO2

Purification of Copper βš’οΈ

Purification occurs through electrolysis, with impure copper as the anode and pure copper as the cathode:

Uses of Copper πŸͺ¨

Zinc πŸͺ¨

Ores: Common ores are zinc blende (ZnS) and calamine (ZnCO3). πŸͺ¨

Extraction of Zinc βš’οΈ

Zinc extraction involves roasting zinc blende to form zinc oxide, which is then reduced with carbon monoxide:

Uses of Zinc πŸͺ¨

Iron πŸͺ¨

Ores: Common ores include hematite (Fe2O3), magnetite (Fe3O4), and siderite (FeCO3). πŸͺ¨

Extraction of Iron in the Blast Furnace βš’οΈ

Iron is extracted from hematite by reduction in a blast furnace, using coke (carbon) as a reducing agent:

Uses of Iron πŸͺ¨

Reactivity Series of Metals πŸ“Š

The reactivity series arranges metals by their reactivity, from most reactive (e.g., potassium) to least reactive (e.g., gold). Metals higher in the series displace those lower in chemical reactions. ⚑

Displacement Reactions πŸ”„

A more reactive metal displaces a less reactive metal from a solution of its compound. For example: