The first ionization energy for rubidium is +403.0 kJ/mol.How much energy would be required to convert 17.1 g of gaseous rubidium to its gaseous +1 monatomic ion at constant temperature?
A)185 kJ
B)80.6 kJ
C)68.9 kJ
D)40.4 kJ
E)34.5 kJ

Question

Quizplus · Accepted Answer

First, we need to convert the mass of rubidium given into moles. 
mass of Rb = 17.1 g 
molar mass of Rb = 85.47 g/mol (from periodic table) 
moles of Rb = 17.1 g / 85.47 g/mol = 0.2001 mol

The energy required to convert 1 mole of gaseous rubidium to its gaseous +1 monatomic ion is equal to its first ionization energy (+403.0 kJ/mol). Therefore, to convert 0.2001 mol of Rb, we need: 
Energy required = 0.2001 mol x (+403.0 kJ/mol) = 80.6 kJ

Therefore, the answer is B, 80.6 kJ.

The First Ionization Energy for Rubidium Is +403