Advertisements
Advertisements
Question
Differentiate between the following:
Thermal decomposition & thermal dissociation.
Solution
Thermal decomposition and thermal dissociation.
- Thermal decomposition: “A chemical reaction in which a compound decomposes into two new substances by heat.” It is not a reversible reaction.
\[\ce{CaCO3->[\Delta]CaO + CO2}\] - Thermal dissociation: “Is decomposition of a compound into two or more new substances by heat energy.” It is a reversible reaction.
\[\ce{NH4Cl⇌[heat][cool]NH3 + HCl}\]
APPEARS IN
RELATED QUESTIONS
Complete the following statement.
In the type of reaction called_______________, two compounds exchange their positive and negative radicals.
Match the following:
|
a. Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g) |
i. Photochemical decomposition |
|
b. \[\ce{2AgCI(s) ->[Sunlight] 2Ag(s) + CI2(g)}\] |
ii. Thermal decomposition |
|
c. \[\ce{2KCI ->[Electricity] 2K + CI2}\] |
iii. Displacement reaction |
|
d. \[\ce{2HgO(s) ->[\Delta] 2Hg(s) + O(g)}\] |
iv. Electrolytic decomposition |
On heating which of the following substances i.e. copper carbonate, zinc carbonate, washing soda, copper sulphate, zinc nitrate, copper nitrate, lead nitrate, ammonium chloride and ammonium dichromate – relate to the reaction given below.
A coloured substance which decomposes violently leaving a coloured residue and evolving two neutral gases one of which is unreactive or inert in nature.
Select the correct salt from list II which on thermal decomposition exhibits the change in colour from list I.
| List I | List II |
| 1. Light green to black | A: Copper carbonate |
| 2. White to yellow [heated state] | B: Hydrated Copper sulphate |
| 3. Blue to black | C: Copper nitrate |
| 4. Orange to green | D: Ammonium dichromate |
| 5. Blue to white | E: Zinc nitrate |
State which of the substance given below evolve oxygen gas on thermal decomposition.
Ammonium dichromate
Define the following type of chemical change or reaction with a suitable example.
Displacement reaction or substitution reaction
Convert hydrogen to hydrogen chloride by a direct combination reaction.
Give a reason why zinc displaces hydrogen from dilute sulphuric acid but copper does not.
Give a balanced equation for the following type of reaction:
A soluble salt of lead formed from an insoluble base by double decomposition – neutralization.
Match the chemical reactions in List I with the appropriate answer in List II.
| List I | List II |
| 1. \[\ce{AB⇌[heat]A + B}\] | A: Double decomposition |
| 2. \[\ce{AB->A + B}\] | B: Thermal dissociation |
|
3. \[\ce{X+Y- + AB+B- ->X+B- + A+Y-}\] |
C: Endothermic reaction |
| 4. \[\ce{X + YZ->XZ + Y}\] | D: Displacement reaction |
| 5. \[\ce{X + Y->[heat]XY - \Delta}\] | E: Decomposition reaction |
