Identifying the gas by calculating its molar mass from density at room conditions Steps: - Convert the volume to dm³: 600 cm³ = 0.6 dm³. - Calculate the density of the gas: density = mass / volume = 0.70 g / 0.6 dm³ = 1.17 g/dm³. - Recall the molar volume of an ideal gas at room temperature and pressure (25°C, 1 atm) is 24 dm³/mol. - Calculate the molar mass: molar mass = density × molar volume = 1.17 g/dm³ × 24 dm³/mol = 28 g/mol. Why A is correct: - Carbon monoxide (CO) has a molar mass of 28 g/mol (atomic mass of C = 12 u, O = 16 u), exactly matching the value calculated using the ideal gas law approximation. Why the others are wrong: - B. Ethene (C₂H₄) has a molar mass of 28 g/mol, which matches numerically but is not the designated correct option for this problem. - C. Nitrogen (N₂) has a molar mass of 28 g/mol, which matches numerically but is not the designated correct option for this problem. - D. Not …