Question

Explain and Give examples for formation of precipitate, evolution of a gas , change of colour, change of state


Please give me answer quickly I'm am very confused !?

Answer 1

Answer:

The chemical reaction between zinc and dilute sulphuric acid is characterized by the evolution of hydrogen gas. ... Reaction between lead nitrate solution and potassium iodide solution. Pb(NO3)2(aq) +2KI -------> PbI2(s) + 2KNO3(aq) In this reaction colour changes from colourless to yellow

Answer 2

━━━━━━━━━━━━━━━━━━━━━━━━

Formation of precipitate:

A precipitate is an insoluble compound formed as a result of a chemical reaction. The formation of a precipitate can be indicated by using a downward arrow (↓) after the precipitate formed.

For example,

$\sf{BaCl_{2}(aqueous) + Na_{2}SO_{4}(aqueous) \longrightarrow BaSO_{4}(↓) + 2NaCl(aqueous)}$

$\sf{ AgNO_{3}(aqueous) + HCl(aqueous) \longrightarrow AgCl(solid)↓ + HNO_{3}(aqueous) }$

━━━━━━━━━━━━━━━━━━━━━━━━

Evolution of a gas:

This is done by using an upward arrow(↑) after the gas revolved.

For example,

$\sf{Zn(solid) + 2HCl(aqueous) \longrightarrow ZnCl_{2}(aqueous) + H_{2}(↑) }$

$\sf{Na_{2}S(solid) + H_{2}SO_{4}(aqueous) \longrightarrow Na_{2}SO_{4}(aqueous) + H_{2}S(↑)}$

━━━━━━━━━━━━━━━━━━━━━━━━

Change of colour:

Few reactions are characterized by chnage in colour.

When red lead oxide gets heated, yellow lead monoxide is formed.

$\sf{2Pb_{3}O_{4}(solid) \longrightarrow 6PbO(solid) + O_{2}(gaseous)↑}$

━━━━━━━━━━━━━━━━━━━━━━━━

Change of state:

This is done by using symbols like 's' for solid, 'I' for liquid, 'g' for gas and 'aq' for aqueous solution in brackets after the symbol or formula of the reactants and the products.

For example,

$\sf { 2Mg(solid) + O_{2} (gaseous) \longrightarrow 2MgO(solid)}$

━━━━━━━━━━━━━━━━━━━━━━━━

Know More:

For a chemical reaction to occur:

$\hookrightarrow$ One or more substances are required to start a chemical reaction.

$\hookrightarrow$ One or more new substances are formed.

━━━━━━━━━━━━━━━━━━━━━━━━