Thermal decomposition mass loss identifies the Group 2 metal nitrate Steps:

• Calculate mass loss fraction: 3.2 g / 5.00 g = 0.64
• Decomposition reaction: M(NO3)₂ → MO + 2NO₂ + ½O₂; mass lost per mole = 108 g
• Molar mass of M(NO3)₂ = 108 g / 0.64 ≈ 169 g/mol; M ≈ 169 - 124 = 45 g/mol
• This value approximates calcium's atomic mass of 40, with 3.2 g loss matching calculated 3.29 g for Ca(NO3)₂ Why B is correct:
• For calcium (M=40), molar mass 164 g/mol yields 108/164 ≈ 0.66 mass loss fraction, giving 3.29 g loss from 5 g—matches observed 3.2 g per decomposition formula Why the others are wrong:
• A. Magnesium (M=24): 108/148 ≈ 0.73 fraction, 3.65 g loss—exceeds 3.2 g
• C. Strontium (M=88): 108/212 ≈ 0.51 fraction, 2.55 g loss—below 3.2 g
• D. Barium (M=137): 108/261 ≈ 0.41 fraction, 2.07 g loss—below 3.2 g

Final answer: B