Question

. Define and give one example for each of the following type of chemical reactions. 1. Combination Reaction. 2. Thermal Decomposition Reaction. 3. Photochemical decomposition reaction. 4. Electrolysis.

Answer 1

• Explanation:

• COMBINATION REACTION: When two or more substances chemically bonded together to produce a single product, it is called as combination reaction or synthesis reaction. When the bond forms between the elements, heat is released; this is because the reactions are usually exothermic.
• Examples :. Na2 + H2O -----> 2NaOH  Here sodium oxide is combined with water gives sodium hydroxide.

• Decomposition reaction: Those reactions in which a compound split into two or more simpler substances are called as decomposition reactions

       Example: The digestion of food in our body is an example of          decomposition  reaction.

• THERMAL DECOMOSITION REACTION:A thermal decomposition reaction occurs when heat is applied to a compound causing it to decompose (break down) into multiple different chemical substances.

• An example is when baking soda (sodium bicarbonate) is heated
• 2 N a H C O 3 ( s ) → C O 2 ( g ) + H 2 O ( g ) + N a 2 C O 3 ( s)
• PHOTOCHEMICAL DECOMOSITION REACTION:When decomposition reaction is carried out by light then it is called photochemical decomposition reaction.
• Example: silver chloride in the presence of light decomposes to give silver and chlorine gas
• ELECTROLYSIS:Electrolysis is the passing of a direct electric current through an ionic substance that is either molten or dissolved in a suitable solvent, producing chemical reactions at the electrodes and decomposition of the materials.
• Example: NaCl molecule will dissociate at higher temperatures, but on electrolysis it will decompose easily. Using electricity the non-spontaneous reactions can also takes place easily.
• Water cannot be dissociated easily by supplying but when electricity it can dissociated into its elements.
• 2H2O→ 2H2 + O2
• 2NaCl → 2Na (at Cathode)+ Cl2 (at anode)
• 2AlCl3 → 2Al (at Cathode) + 3 Cl2 (at anode)
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