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Edexcel A-Level Chemistry AS 8.16 The Reasons for the Trends in Thermal Stability of the Nitrates and the Carbonates of the Elements in Groups 1 And 2 Questions

A smaller or more highly charged cation polarises the anion more strongly, weakens its internal bonds and lowers the decomposition temperature or stability.

Syllabus
First assessment 2019
Course
Chemistry YCH11
Level
AS

Exam points

  • Explain stability trends using cation radius, charge density and anion polarisation.
  • Write balanced thermal-decomposition equations for Group 1 or 2 nitrates and carbonates.
  • Interpret temperatures or graphs to compare decomposition and convert units where required.

Edexcel A-Level Chemistry AS 8.16 The Reasons for the Trends in Thermal Stability of the Nitrates and the Carbonates of the Elements in Groups 1 And 2 Questions question 1

[Maximum number: 3]

Magnesium ethanedioate ( MgC2O4\mathrm{MgC}_{2} \mathrm{O}_{4} ) decomposes on gentle heating to form magnesium carbonate and carbon monoxide.

MgC2O4→MgCO3+CO\mathrm{MgC}_{2} \mathrm{O}_{4} \rightarrow \mathrm{MgCO}_{3}+\mathrm{CO}

Magnesium carbonate undergoes thermal decomposition at a higher temperature than magnesium ethanedioate.

MgCO3→MgO+CO2\mathrm{MgCO}_{3} \rightarrow \mathrm{MgO}+\mathrm{CO}_{2}

Explain the trend in the thermal decomposition of Group 2 carbonates going down the group.

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