Question

Consider this reaction involving an unknown element X. F, +2 XBr Brı + 2 XF When 2.700 g of XBr reacts, 1.504 g of Br, is produced. Calculate the molar mass of X, and then identify its element symbol

Answer 1

The molar mass of the unknown element X in the compound XBr is calculated to be approximately 63.716 g/mol. By comparing this to the periodic table, the element is identified as Copper (Cu) with a molar mass of about 63.546 g/mol.

Step-by-step explanation:

To find the molar mass of the unknown element X in the compound XBr, we can use the given mass of XBr and the produced Bromine. We start by finding the moles of Br2 produced using its molar mass (159.808 g/mol). Since 1.504 g of Br2 is produced, we can calculate the moles of Br2 as follows:

1.504 g Br2 × (1 mol Br2 / 159.808 g Br2) = 0.0094 moles of Br2

From the balanced equation, we see that 1 mole of XBr produces 0.5 moles of Br2. Therefore, the moles of XBr reacted is twice the moles of Br2 produced, which is 0.0094 × 2 = 0.0188 moles of XBr.

Now, we use the mass of XBr (2.700 g) and the moles of XBr (0.0188 mol) to calculate the molar mass of XBr:

Molar Mass of XBr = 2.700 g / 0.0188 mol = 143.62 g/mol

The molar mass of Br is 79.904 g/mol, so we can find the molar mass of X by subtracting the molar mass of Br from the molar mass of XBr:

Molar Mass of X = Molar Mass of XBr - Molar Mass of Br = 143.62 g/mol - 79.904 g/mol = 63.716 g/mol

Looking at the periodic table, we can identify the element with a molar mass closest to 63.716 g/mol. This element is Copper (Cu), with a molar mass of about 63.546 g/mol.

Answer 2

To find the molar mass of element X in XBr, the moles of Br2 produced are calculated and used to determine the moles and then the molar mass of XBr. Subtracting the molar mass of bromine from the molar mass of XBr gives the molar mass of X, which is close to that of Iodine (I).

Step-by-step explanation:

To calculate the molar mass of element X in the compound XBr, we first determine the mass of Br2 produced. Since 1.504 g of Br2 is produced, we can calculate the moles of Br2, which is diatomic and has a known molar mass of approximately 159.808 g/mol (79.904 g/mol for each bromine atom).

1.504 g Br2 × (1 mol Br2/159.808 g Br2) = 0.00941 mol Br2

The reaction shows that one mole of XBr produces one mole of Br2, so 0.00941 mol of XBr also reacted. Then, we use the initial mass of XBr to find the molar mass of XBr:

2.700 g XBr × (1 mol XBr/0.00941 mol XBr) = 287.14 g/mol for XBr

After subtracting the molar mass of two bromine atoms from the molar mass of XBr, we can find the molar mass of X:

287.14 g/mol XBr - 159.808 g/mol Br2 = 127.332 g/mol for X

Looking at the periodic table, the element with a molar mass close to this value is Iodine (I), with an atomic mass of about 126.9 g/mol.