To determine the formula for compound X, we need to analyze the products formed during its decomposition.
From the given information, we know that the cylinder contains 0.3 mol of carbon dioxide (CO2), 0.25 mol of liquid water (H2O), 0.025 mol of oxygen gas (O2), and an undetermined amount of a gaseous element A.
To determine the formula for X, we need to calculate the molar ratio between the moles of carbon dioxide and the moles of element A.
Since the 0.3 mol of carbon dioxide comes from the decomposition of compound X, we can assume that the same number of moles of element A is also produced.
Therefore, the formula for compound X is likely CnA, where n is the number of carbon atoms and A represents the gaseous element.