Question

If a student weighs out 0.744 g Fe ( NO 3 ) 3 ⋅ 9 H 2 O , what is the final concentration of the ∼0.2 M Fe ( NO 3 ) 3 solution that the student makes?

Answer 1

Molar concentration of Fe(NO3)3 . 9H2O = 0.12M

Step-by-step explanation:

Fe(NO3).9H2O --> Fe(NO3)3 + 9H2O

By stoichiometry,

1 mole of Fe(NO3)3 will be absorb water to form 1 mole of Fe(NO3)3 . 9H2O

Therefore, calculating the mass concentration of Fe(NO3)3;

Molar mass of Fe(NO3)3 = 56 + 3*(14 + (16*3))

= 242 g/mol

Mass concentration of Fe(NO3)3 = molar mass * molar concentration

= 242 * 0.2

= 48.4 g/L

Molar mass of Fe(NO3)3 . 9H2O = 56 + 3*(14 + (16*3)) + 9* ((1*2) + 16)

= 242 + 162 g/mol

= 404g/mol

Concentration of Fe(NO3)3 . 9H2O = mass concentration/molar mass

= 48.4 /404

= 0.12 mol/l

Molar concentration of Fe(NO3)3 . 9H2O = 0.12M