Question

Consider this reaction involving an unknown element X.

F2+2XBr⟶Br2+2XF
When 1.900 g of XBr reacts, 1.095 g of Br2 is produced.
a.Calculate the molar mass of X, and then identify its element symbol.

Answer 1

The molar mass of X is calculated by first finding the moles of Br2 produced, then using this to find the moles and molar mass of XBr, from which the molar mass of element X is calculated by subtraction. X is identified as Cobalt (Co) based on the approximate atomic mass of 58.78 g/mol.

Step-by-step explanation:

To calculate the molar mass of element X, first we need to convert the mass of Br2 produced into moles using its molar mass (159.808 g/mol):

1.095 g Br2 × (1 mol Br2 / 159.808 g Br2) ≈ 0.00685 mol Br2

According to the balanced chemical equation, 2 moles of XBr produce 1 mole of Br2, so the moles of XBr reacted is 0.00685 mol × 2 ≈ 0.0137 mol XBr.

To find the molar mass of XBr:

1.900 g XBr / 0.0137 mol XBr ≈ 138.69 g/mol

To find the atomic mass of X, we subtract the molar mass of Br from the molar mass of XBr:

138.69 g/mol - 79.904 g/mol (atomic mass of Br) ≈ 58.78 g/mol

This is approximately the atomic mass of Cobalt (Co), which points to X being the element Cobalt.