Final answer:
The atomic mass of element X is found by deducting the mass of hydrogen from the molar mass of X4H10 gas (which is twice the average molar mass of air) and dividing by the number of X atoms. It is 12 grams per mole.
Step-by-step explanation:
The question is asking for the atomic mass of element X, given that the relative density of X4H10 gas compared to air is 2. To solve this, we can use the concept of relative density and molar mass. Relative density is the ratio of the density of a gas to the density of air. Since air has an average molar mass of approximately 29 g/mol, and the relative density of X4H10 to air is 2, we can deduce that the molar mass of X4H10 is twice that of air, which is 58 g/mol (2 times 29 g/mol).
To find the atomic mass of X, we subtract the mass of the hydrogen atoms from the molar mass of X4H10. This means subtracting 10 times the atomic mass of hydrogen (1.008 g/mol) from 58 g/mol, which gives us 48 g/mol for four atoms of X. Dividing 48 by 4 gives us the atomic mass of one atom of X, which is 12 g/mol. Therefore, the atomic mass of element X is 12 grams per mole.