Question

what is reaction ? how many types of reaction are there ?

Answer 1

Answer:

A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another.

The main four types of reactions are direct combination, analysis reaction, single displacement, and double displacement.

Answer 2

Chemical reaction is a process in which one or more substances undergo trans-formation to form new substances with different properties.

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• ${\bold { \underline{\small{Reactants -}}}}$ substances which take part in a chemical reaction.

• ${\bold { \underline{\small{Products -}}}}$ substances which are formed after the chemical reaction.

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$\underline{\underline{\maltese\:\: \textbf{\textsf{Types\: of\: Reactions}}}}$

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${\bold { \underline{\small{1.\: Decomposition\: reactions :}}}}$ In these reactions, compound either of its own or upon heating decomposes to give two or more components out of which at least one is in the elemental state.

$\:\:\:\:\:\:\:\:\:\:\:\:\:\:$$\sf 2NaH(s)$ $\overset{\Delta}{\longrightarrow}$ $\sf 2Na(s)+H_2(g)$

$\:\:\:\:\:\:\:\:\:\:\:\:\:\:$$\sf 2H_2O(l)$ $\overset{\Delta}{\longrightarrow}$ $\sf 2H_2(g)+O_2(g)$

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${\bold { \underline{\small{2.\: Combination\: reactions : }}}}$ In combination reactions, compounds are formed as a result of the chemical combination of two or more elements.

$\:\:\:\:\:\:\:\:\:\:\:\:\:\:$$\sf H_2(g)\:+$ $\bf\dfrac{1}{2}$ $\sf O_2(g)$ $\longrightarrow$ $\sf H_2O(l)$

$\:\:\:\:\:\:\:\:\:\:\:\:\:\:$$\sf C (s)\:+$ $\sf O_2(g)$ $\longrightarrow$ $\sf CO_2(g)$

$\:\:\:\:\:\:\:\:\:$$\sf 3Mg (s)\:+$ $\sf N_2 (g)\:+$ $\longrightarrow$ $\sf Mg_3N_2(s)$

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${\bold { \underline{\small{3.\: Displacement \:reactions : }}}}$ In these reactions, an atom/ion present in a compound gets replaced by an atom/ion of another element.

$\sf FeSO_4(aq)+$ $\sf Zn(s)$ $\longrightarrow$ $\sf ZnSO_4(aq)\:+$ $\sf Fe(s)$

$\sf MgO(aq)\:+$ $\sf 2Na(s)$$\longrightarrow$ $\sf Na_2O(aq)\:+$ $\sf Mg(s)$

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${\bold { \underline{\small{ 4.\: Disproportionation\: reactions :}}}}$ The chemical reaction in which only one substance is oxidized as well as reduced simultaneously is called disproportionation reaction.

$\sf Cl_2\:+$ $\sf 2NaOH$ $\longrightarrow$ $\sf\ NaCl+NaOCl+H_2O$

$\sf\small P_4 \:+\:NaOH\:+2H_2O$ $\longrightarrow$ $\sf\small 2NaH_2PO_2\:+2PH_3$

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${\bold { \underline{\small{ 5.\: Substitution \:reaction :}}}}$ In these reactions, one or more atoms or groups present in organic molecule get substituted or replaced by suitable atoms or groups.

${C_2H_5Cl} \atop {Ethyl\: chloride}$+$\sf\small KOG(aq)$ $\longrightarrow$ ${C_2H_5OH} \atop {Ethyl\: alcohol}$+$\sf\small KCL$

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${\bold { \underline{\small{ 6.\: Neutralisation \:reaction : }}}}$ when an acid reacts with a base, salt and water is formed. This reaction is called neutralisation reaction.

$\:\:\:\:\:\:\:\:\:$$\sf acid\:+\:base$ $\longrightarrow$ $\sf salt\:+\:water$

$\:\:\:\:\:\:\:\:$$\sf HCl\:+\:NaOH$ $\longrightarrow$ $\sf NaCl\:+\:H_2O$

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${\bold { \underline{\small{ 7.\: Reversible\: reaction :}}}}$ a reaction in which reactants combined to form products and again products recombined to reactants is called reversible reaction.

$\:\:\:\:\:\:\:\:\:\:\:\:$$\sf N_2(g)\:+\:3H_2(g)$ $\rightleftharpoons$ $\sf 2NH_3(g)$

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${\bold { \underline{\small{ 8.\: Irreversible\: reaction :}}}}$ a reaction which proceeds in only one direction is called irreversible reaction.

$\:\:\:\:\:\:\:\:$$\sf CaCO_3(s)$ $\overset{\Delta}{\longrightarrow}$ $\sf CaO(s)+CO_2(g)$

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$\textbf{MORE\:TO\: KNOW\:-}$

$\normalsize\textit{\:\:\:\:Characteristics\: of\: chemical \:reactions}$

• $\small\red{ \large\star}$$\sf Change\:in\:temperature$

• $\small\purple{ \large\star}$$\sf Change\:in\:colour$

• $\small\pink{ \large\star}$$\sf Evolution\:of\:a\:gas$

• $\small\gray{ \large\star}$$\sf Formation\:of\:a\: precipitate$

• $\small\orange{ \large\star}$$\sf Change\:in\: physical\:state$