An alloy of metals X and Y weighs 12 g & contains atoms X and Y in the ratio of 2 : 5 . The percentage of Metal X in the alloy is 20 by mass. If the atomic mass of X is 40 , what is the atomic mass of metal Y.

Step-by-step solution

According to mole concept Mass of metal X in alloy =   12 × 20 100 Mass of metal Y in alloy =   12 - 2 . 4   = 9 . 6   g Moles of X =   2 . 4 40 Now, Number of atoms of X   =   2 . 4 40 × 6 . 023 × 10 23   =   3 . 61 × 10 22 Number of atoms of Y   =   3 . 61 × 10 22 × 5 2   =   9 . 025 × 10 22 Thus, by the stoichiometry 9 . 6 g   Y   → 9 . 025 × 10 22   atom 6 . 022 × 10 23 → 9 .