Thermal decomposition of calcium nitrate

Steps:

• Write the balanced equation: Ca(NO₃)₂ → CaO + 2NO₂ + ½O₂.
• Identify gaseous products: NO₂ and O₂.
• For 1 mol Ca(NO₃)₂, produce 2 mol NO₂ and 0.5 mol O₂.
• Total gas: 2 + 0.5 = 2.5 mol.

Why C is correct:

• The stoichiometry of the decomposition equation yields 2.5 mol of gas (2 NO₂ + 0.5 O₂) per mole of Ca(NO₃)₂.

Why the others are wrong:

• A: Ignores all oxygen gas produced.
• B: Counts only NO₂, omitting 0.5 mol O₂.
• D: Overcounts, possibly mistaking for ammonium nitrate decomposition.

Final answer: C