D.
Gastropods live in every conceivable habitat
Answer is: the ratio of amount NaOH reacting per unit amount FeCl₃ is 3 mol NaOH /1 mol FeCl₃.
Balanced chemical reaction:
3NaOH(aq) + FeCl₃(aq) → 3NaCl(aq) + Fe(OH)₃(s).
NaOH is sodium hydroxide.
FeCl₃ is iron(III) chloride.
Coefficient for sodium hydroxide is three and for iron(III hydroxide is one.
H - 1.01
C - 12.01
0 - 16.00
2(1.01) + 12.01 + 2(16.00) = 46.03 g/mol
Density = mass/volume = 316/22.5 = 14.045g/mL.