AP CHEMISTRY GAS LAWS l

Question

A sample of Group 1 bromide weighing 2.000 g was converted to a gas at 504.0 degrees C and 1.000 atm pressure. The resulting vapor occupied a volume of 1238 mL. Identify the Group 1 metal present in the compound.

Answer 1

To find the identity of the group 1 metal, we need to find mols of gas and then find mass of gas. Then, knowing atomic mass of Br, we can deduce the identity of the metal.

PV = nRT

n = moles = PV/RT

n = (1.000 atm)(1.238 L) / (0.0821 Latm/Kmol)(777K)

n = 0.01941 moles of XBr gas

molar mass of XBr = 2.000 g / 0.01941 mols = 103.0 g/mol

Br = 79.9

XBr = 103.0 - 79.9 = 23.1

X = Na (sodium)