Question

For the following reaction between Mohr\'s salt (iron as FeSO4(NH4)2SO4

Answer 1

Given Molarity of potassium dichromate is , M = 0.290 M

         Volume of potassium dichromate , V = 0.0500 L

So number of moles of potassium dichromate is n = Molarity x volume in L

                                                                         = 0.290 M x 0.0500 L

                                                                         = 0.0145 mol

The balanced reaction is Cr₂O₇^2- + 6Fe²⁺ + 14H⁺ --> 2Cr³⁺ + 6Fe³⁺+ 7H₂O

From the above reaction ,

1 mole of potassium dichromate reacts with 6 moles of Mohr's salt

0.0145 mol of potassium dichromate reacts with 6x0.0145 moles of Mohr's salt

                                                                       = 0.087 moles of Mohr's salt

Given molarity of Mohr's salt is M'=0.290 M

So volume of Mohr's salt reacted is , V' = number of moles of Mohr's salt / Molarity of Mohr's salt

                                                         = 0.087 mol / 0.290 M

                                                         = 0.3 L

                                                         = 0.3 x 1000 mL

                                                         = 300 mL

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Similarly for the second case:

Number of moles of Mohr's salt = Molarity x volume in L

                                              = 0.290 M x 0.0500 L

                                              = 0.0145 mol

From the above reaction ,

1 mole of potassium dichromate reacts with 6 moles of Mohr's salt

Z mol of potassium dichromate reacts with 0.0145 mol moles of Mohr's salt

   

  volume of potassium dichromate reacted is ,

    V' = number of moles of potassium dichromate / Molarity of potassium dichromate

        = 0.00242 mol / 0.290 M

        = 0.3 L

        = 0.00833 x 1000 mL

        = 8.3 mL