Asample of iron metal is placed in a graduated cylinder. it is noted that 10.4 ml of water is displaced by the iron. the iron is then reacted with excess hydrochloric acid to produce iron (ii) chloride and hydrogen gas. given the density for iron is 7.86 g/ml, how many grams of iron (ii) chloride are produced in the reaction?

                 162.43 g of FeCl₂

Step 1: Calculate mass of Fe;

As,

                                   Density  =  Mass ÷ Volume

Or,

                                   Mass  =  Density × Volume

Where Volume is the volume of water displaced  =  10.4 mL

Putting values,

                                   Mass  =  7.86 g.mL⁻¹ × 10.4 mL

                                   Mass  =  81.744 g of Fe

Step 2: Calculate amount of FeCl₂;

The balance chemical equation is as follow,

                                Fe  +  2 HCl   →    FeCl₂  +  H₂ ↑

According to this equation,

       55.85 g (1 mol) Fe produced  =  110.98 g (1 mol) of FeCl₂

So,

               81.744 g Fe will produce  =  X g of FeCl₂

Solving for X,

                    X  =  (81.744 g × 110.98 g) ÷ 55.85 g

                     X =  162.43 g of FeCl₂

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