Thermal decomposition of Group 2 nitrates

Steps:

• Group 2 nitrates decompose on heating to form metal oxide, nitrogen dioxide, and oxygen.
• General formula: 2M(NO₃)₂ → 2MO + 4NO₂ + O₂, where M is the Group 2 metal.
• For radium (Ra), substitute into the formula.
• Balance atoms: left side has 2 Ra, 12 O, 4 N; right side matches with 2 RaO (2 Ra, 2 O), 4 NO₂ (4 N, 8 O), O₂ (2 O).

Why A is correct:

• Matches the standard balanced equation for Group 2 nitrate decomposition, conserving atoms per the law of conservation of mass.

Why the others are wrong:

• B: Unbalanced; uses single molecule but produces half O₂, violating atom conservation.
• C: Produces NO (nitric oxide) instead of NO₂ (nitrogen dioxide), incorrect for strong heating.
• D: Produces 8 NO₂, exceeding nitrogen atoms and unbalancing the equation.

Final answer: A