The number of sulfate ions that are in 100 ml of a solution of 0.0020 M Fe2(SO4)3 is 6 x10 ^-4 moles
calculation
find the moles of Fe2(SO4)3 that dissociated
moles = molarity x volume in liters
volume in liters = 100/1000 = 0.1 liters
molarity =0.002 M
moles = 0.002 x0.1 =2 x10 ^-4 moles
write the equation for dissociation
Fe2(SO4)3 = 2fe^3+ + 3 SO4^2-
by use of mole ratio between Fe2(SO4)3 to SO4^2- which is 1:3 therefore the moles of SO4^2- is
= 0.0002 x3 = 6 x10 ^-4 moles
