Thermal Decomposition

Question 1

What is thermal decomposition

Answer 1

Chemical reaction that happens when a compound breaks down when heated

Question 2

Thermal decomposition of group 2 carbonates

Answer 2

Forms metal oxide (solid) and carbon dioxide (gas)

Question 3

Thermal decomposition of group 2 metals nitrates

Answer 3

-form metal oxide (solid) and nitrogen dioxide (brown gas) and oxygen (gas)

Question 4

Why does thermal stability increase down group 2

Answer 4

-cation gets bigger going down the group as there are more shells of electrons
-small cation has high charge density (due to small ionic radii)
-the small cation polarises the electron cloud on the anion(CO3/NO3)to a greater extent
-this weakens the N-O/C-O bond and therefore less energy is required to break it
-this means the compound is more likely to break apart into NO2/CO2/O2

Question 5

How does thermal decomposition change down group 1

Answer 5

-become more thermally stable down group but need more energy to decompose compounds

Question 6

Thermal decomposition of group 1 carbonates

Answer 6

Li2CO3 ——>Li2O+CO2
Na and K- no reaction

Question 7

What do hydrated compounds give off upon heating

Answer 7

Fairly gentle heating causes most to give off water vapour and form anhydrous compound

Question 8

Does an increase in thermal stability mean more or less energy is needed for the reaction

Answer 8

Means more heat is required

Question 9

Which group 1 element reacts in same way as group 2 in thermal decomposition

Answer 9

Lithium does for carbonate and nitrate

Question 10

What is formed when group 1 nitrates thermally decompose

Answer 10

Forms metal nitrite (XNO2) and oxygen

Question 11

Do group 1 carbonates apart from lithium thermally decompose

Answer 11

Do not as would need extremely large amount of energy so reactions do not go to completion