Electrolyte

Electrolyte

Electrolytes are also called “Electrolytic Conductors”.

“Electrolytes are electrovalent substances that form ions in solution which conduct an electric current.”
In other words, 
“An electrolyte is any substance containing free ions that make the substance electrically conductive.”

or

“Electrolytes are any substance that dissociates into ions when dissolved in a suitable medium or melted and thus forms a conductor of electricity.”

The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible. The most familiar electrolytes are acids, bases, and salts, which ionize when dissolved in such solvents as water or alcohol. Many salts, such as sodium chloride, behave as electrolytes when melted in the absence of any solvent; and some, such as silver iodide, are electrolytes even in the solid state.

Example:

Sodium Chloride, Copper Sulphate, Potassium Nitrate
Electrolytes are of two kinds:

1. Strong Electrolyte
2. Weak Electrolyte

Strong Electrolyte

A strong electrolyte is a solute that completely, or almost completely, ionizes or dissociates in a solution.
The solution will contain only ions and no molecules of the electrolyte. Strong electrolytes are good conductors of electricity.

Examples of Strong Electrolytes

Strong Acid

• Perchloric acid(HClO₄)
• Hydriodic acid (HI)
• Hydrobromic acid (HBr)
• Hydrochloric acid (HCl)
• Sulfuric acid (H₂SO₄)
• Nitric acid (HNO₃)
• Chloric acid (HClO₃)
• Bromic acid (HBrO₃)

Strong Base

• Potassium hydroxide (KOH)
• Barium hydroxide [Ba(OH)₂]
• Caesium hydroxide (CsOH)
• Sodium hydroxide (NaOH)
• Strontium hydroxide [Sr(OH)₂]
• Calcium hydroxide [Ca(OH)₂]
• Rubidium hydroxide (RbOH)
• Magnesium hydroxide [Mg(OH)₂]

Salts

• Sodium chloride
• Potassium nitrate
• Magnesium chloride
• Sodium acetate

Weak Electrolyte

A weak electrolyte is an electrolyte that does not completely dissociate in solution, rather undergoes partial ionization or dissociation.
The solution will contain both ions and molecules of the electrolyte. Here, in solution the ions and the dissociated molecules will be in equilibrium with each other. When such a solution is diluted, the degree of ionization increases. It becomes complete at infinite dilution.

Examples:

HCOOH, CH₃COOH, NH₄OH, CH₃NH₂, CH₃COONH₄, H₃PO₄ etc.

Limitations of the Arrhenius Concept of Acids & Bases

Limitations of the Arrhenius Concept of Acids & Bases

Despite its successes, the Arrhenius concept/definition of acids and bases proved to be inadequate for several reasons. 

•   It is and was recognized that acid-base reactions also take place in solvents other than water. But the Arrhenius concept is not applicable for non-aqueous solutions,i.e., it cannot explain the properties of acids and beses in abscence of water.

• Compounds which do not contain hydrogen can release H⁺ ion by reacting with water. For instance, 

• Some bases do not contain OH^- ions. For example, NH₃, CaO etc.

• It is also believed that a H⁺ ion cannot exist in free state in any solvent because of its high charge density. A hydrogen ion would combine with one or more molecules of the solvent. In the case of water as solvent H⁺ ion would combine with water molecule to form what is known as a hydronium/hydroxonium/oxonium ion(H₃O⁺).

These facts together with the studies on the catalysis by acids and bases suggested that the ideas of Arrhenius were inadequate and had to be modified.

Arrhenius Concept of Acids & Bases

    Swedish scientist Svante Arrhenius first explained the cause of acidity and basicity in 1884, with his concept known as the ‘Arrhenius Concept of Acids and Bases’.

The Arrhenius concept of acids and bases can be stated as follows:

     "An acid is a hydrogen containing substance which yields H⁺ (i.e. hydronium ion,H₃O⁺) or increases the concentration of H₃O⁺ (aq.) when dissolved in water."

Example:

     HCl is an acid according to the Arrhenius concept, because it produces or yields H₃O⁺ ion in water.

   According to the Arhenius concept, 

     "A base is a substance which contains hydroxide(OH^-) ion and produces/yields OH^- ion dissolved in water."

 Example:

      NaOH is a base according to the Arrhenius concept of acids and bases, because it produces OH^- ion in water.

Carbonyl Compounds

Carbon-Oxygen Double Bond

   Carbonyl compounds, that is, aldehydes and ketones, are classes of organic compounds which contain a carbon atom doubly bonded to oxygen.

   The functional group of carbonyl compounds is the carbonyl group, which determines the chemistry of these compounds and this is why aldehydes and ketones are collectively called carbonyl compounds.

•  In aldehydes, the carbonyl carbon is linked to one hydrogen atom and one alkyl group(Formaldehyde, in which -CO is joined to two H atoms being an exception).

• On the other hand, in ketones, the -CO group is linked to two alkyl groups.

   The carbonyl group is made up of a sigma bond and a pi-bond. It is polar due to oxygen's greater electronegativity.

Epsom Salt

General Information

Magnesium sulphate heptahydrate is commonly known as Epsom Salt. The molecular formula of Epsom Salt isMgSO₄. 7H₂O. Epsom salt, named for a bitter saline spring at Epsom in Surrey, England, is not actually salt but a naturally occurring pure mineral compound of magnesium and sulfate. It is often called heptahydrate epsomite or soaking salt.

It is white in colour, salty in odour,, efflorescent crystalline substance.Crystalline Epsom loses water on heating forming anhydrous magnesium sulphate.

Occurrence

Magnesium sulphate occurs in nature as,

Kieserite MgSO₄.H₂O

Epsomite MgSO₄.7H₂O (in certain gypsum deposits).

It is also present in certain mineral springs.

Laboratory Preparation

In laboratory, magnesium sulphate is prepared by dissolving magnesium, its oxide, hydroxide or carbonate in dilute sulphuric acid and evaporating the resulting solution, when colorless efflorescent crystals of the heptahydrate, MgSO4.7H2O, crystallize out.

It is less soluble in cold water but soluble on boiling.

Uses:

·         In medicine as mild purgative.

·         In industry as a weighing material for cotton and silk.

·         In fire-proofing fabrics.

·         As a filler for paper.

·         As a mordant- in dyeing and in tanning industry.

·         In the manufacture of soaps and paints.

health benefits of using Epsom salt

01.  Eases stress and relaxes the body

02.  Relieves pain and muscle cramps

03.  Helps muscles and nerves function properly

04.  Helps prevent hardening of arteries and blood clots

05.  Makes insulin more effective

06.  Relieves constipation

07.  Eliminates toxins from the body

Isochoric Process

 Definition

An isochoric process, also called a constant-volume process, an isovolumetric process, or an isometric process, is a thermodynamic process, in which the volume of the closed system is kept or held constant.

Fig: Isochoric Process

For an isochoric process, dV=0. In this process, the work done by the system is zero, i.e., W=0

Therefore from first law of thermodynamics, ΔQ = ΔU as the net work done Wisochoric = 0. Thus in an isochoric process, the total heat energy absorbed by the system is used to change its internal energy.

Isobaric Process

The term ‘Isobaric’ derives from the Greek isos(equal), and barus(heavy).  

An isobaric process is a thermodynamic process, in which the pressure of the working system remains/maintained/kept constant throughout the process.

In an isobaric process, dP=0. Hence, V/T is constant in an isobaric process.

          W =   PdV = PΔV = nRΔT(where n is number of moles)

In an isobaric process, there are typically internal energy changes, work is done by the system, and heat is transferred, so none of the quantities in the first law of thermodynamics readily reduce to zero.

 This is usually obtained by allowed the volume to expand or contract in such a way to neutralize any pressure changes that would be caused by heat transfer

Isothermal Process

Definition

'Isothermal' means at constant temperature. An isothermal process may be defined as follows, “An isothermal process is a thermodynamic process or change of a system,in which the temperature is maintained constant during supply of heat energy.”

Fig: Isothermal process

       In any isothermal process, ΔT = 0 and Q ≠ 0 . This typically occurs when a system is in contact with an outside thermal reservoir (heat bath), and the change occurs slowly enough to allow the system to continually adjust to the temperature of the reservoir through heat exchange.

       In such a case heat is allowed to flow from the surroundings into the system during expansion of gas, and taken out from the system to the surroundings during compression of the gas.

       An isothermal process is carried out by placing the system in a thermostat(constant temperature bath).

 Example

A practical example of isothermal process is some heat engines which work on the basis of the carnot cycle. The carnot cycle works on the basis of isothermal. 

Some extra info just to learn, not for exam 

•   In a strict sense, an isothermal process must be a reversible process because by definition, if every part of the system is at the same, constant temperature throughout the process, there can be no frictional or other irreversible effects giving rise to heat and causing local changes in temperature. No real process can be perfectly isothermal, some come very close, especially if it is accepted that it is only the spatially-averaged temperature which must remain constant.

•   In processes operating on a single phase, heat transfer will result in a change in temperature unless exactly balanced by some other energy transfer, e.g., work, and this balance can be very difficult to achieve in practice. One solution might be to eliminate the heat transfer: but in reality, insulation can reduce heat transfer but cannot stop heat transfer completely. An alternative approach is to use systems which can accept some heat transfer without a change in temperature.

•   In two-phase systems, heat transfer can be accommodated without changing the temperature by altering the relative amounts of the two phases present. The most common example is a phase equilibrium in a pure substance at constant pressure. Ice in water is frequently used as a fixed point for temperature because this system remains at a constant temperature provided the pressure is constant and the rate of heat transfer is not sufficient to cause the system to depart significantly from equilibrium.