Class 10 Some important properties of acids and bases

### Topics to be covered

=> Conduction of electricity in acids and bases
=> Reaction of acids and bases in water solution
=> What happens when water reacts with acid and base

### CONDUCTION OF ELECTRICITY IN ACIDS AND BASES

color{green}("𝐎𝐁𝐒𝐄𝐑𝐕𝐀𝐓𝐈𝐎𝐍 :")

color{green}(★) Bulb will start glowing. This indicates there is flow of electricity in color{red}(HCl) solutions. When some dilute color{red}(HCl) is poured in beaker,it gets ionized and produces color{red}(H^+) and color{red}(Cl^-).

color{red}(HCl (aq) → H^(+) + Cl^(-))

color{green}(★) Hydrogen ion reacts with water and forms hydronium ions.

color{red}(H^(+) + H_2O → H_3^(+) O)

These chloride ions and hydronium ions can move in solution for the conduction of electricity.

### REACTION OF ACIDS AND BASES IN A WATER SOLUTION

color{green}("𝐎𝐁𝐒𝐄𝐑𝐕𝐀𝐓𝐈𝐎𝐍 :") Hydrogen ions in color{red}(HCl) are produced in the presence of water. The separation of color{red}(H^+) ion from color{red}(HCl) molecules cannot occur in the absence of water.

color{red}(HCl + H_2O → H_3 O^(+) + Cl^(-))

Hydrogen ions cannot exist alone, but they exist after combining with water molecules. Thus hydrogen ions must always be shown as color{red}(H^(+) (aq)) or hydronium ion color{red}((H_3O^+ )).

color{red}(H^(+) + H_2O → H_3 O^(+))

color{green}("𝐑𝐄𝐀𝐂𝐓𝐈𝐎𝐍 𝐎𝐅 𝐁𝐀𝐒𝐄𝐒 𝐈𝐍 𝐖𝐀𝐓𝐄𝐑 :")

color{red}(NaOH(s) overset(H_2O)→ Na^(+)(aq) + OH (aq))

color{red}(KOH (s) overset(H_2O)→ K^(+) (aq) + OH^(-) (aq))

color{red}(Mg(OH)_2 (s) overset(H_2O)→ Mg^(2+) (aq) + 2 OH(aq))

Bases generate hydroxide color{red}((OH^– )) ions in water. Bases which are soluble in water are called alkalis.

color{red}(" 𝐉𝐔𝐒𝐓 𝐅𝐎𝐑 𝐂𝐔𝐑𝐈𝐎𝐔𝐒")

All bases do not dissolve in water. An alkali is a base that dissolves in water . They are soapy to touch , bitter and corrosive . Never taste or touch them as they may cause harm. Which of the bases in the table 2.1 are alkalis ?

So from above discussion we inferred that all acids generate color{red}(H^+) ions (aq) and all bases generate color{red}(OH^- (aq)). So neutralization reaction can also be observed as:

color{red}("𝐀𝐜𝐢𝐝 + 𝐁𝐚𝐬𝐞 → 𝐒𝐚𝐥𝐭 + 𝐖𝐚𝐭𝐞𝐫")

color{red}(H X + M OH → MX + HOH)

color{red}(H^(+) (aq) + OH^(-) (aq) → H_2O (l))

### WHAT HAPPENS WHEN WATER IS MIXED WITH ACID AND BASE

When concentrated nitric acid or sulphuric acid is dissolved with water, the reaction is highly exothermic one. The acid must always be added slowly to water with constant stirring. But if water is added to a concentrated acid, the heat generated may cause the mixture to splash out and cause burns. The glass container may also break due to excessive local heating. There is always a warning sign on the
can of concentrated sulphuric acid and on the bottle of sodium hydroxide pellets.

Mixing an acid or base with water results in decrease in the concentration of ions color{red}((H_3O^+//OH^– )) per unit volume. Such a process is called dilution and the acid or the base is said to be diluted.