Question

Consider this reaction involving an unknown element X. F + 2 XBr Br + 2 XF When 5.700 g of XBr reacts, 3.827 g of Br, is produced. Calculate the molar mass of X, and then identify its element symbol. molar mass of X: g/mol element symbol for X:

Answer 1

reaction is F2 + 2XBr --------> Br2 + 2XF

5.700 g of XBr reacts and 3.827 g of Br2 formed

molecular weight of Br2 = 159.808 g/mol

moles of Br2 formed = 3.827/159.808 = 0.0239 mol

so according to the reaction moles of XBr = 2* 0.0239 = 0.0478 mol

weight of XBr = 5.700 g = 0.0478 mol

molecular weight of XBr = weight of XBr / moles of XBr = 5.700 g / 0.0478 mol = 119.247 g/mol

so molar mass of X = 119.247-79.904 = 39.343 g/mol

so the element is Potassium (K)