Question

A solution contains Cr3+ and Mg2+. The addition of 1.00 L of 1.51 M NaF solution is required to cause the complete precipitation of these ions as CrF3(s) and MgF2(s). The total mass of the precipitate is 50.1 g .

Find the mass of Cr3+ in the original solution.

Answer 1

Molar mass of Mg F2= 62.3018 g/mole Molar mass & EvFz= 108.gg gl mole no. of moles S NAF = no. of moles O O = 1.51 M X 102 = 1.51 hole Let the mass of CB = ng Mass MgER (501-X) - no. of moles y trz= x mole 105.33 no. of moles of Mg 5 = 50.1-re 62.3015 . no. of hole of FO ured in Ertz - 3xx 103.99 105.99 3 % lo FE of moles 36.33 FO used no. in Mg F - २ (50. 1-X) ६२.3015 50.1- 31.1505 (56.1-X) -- 151 35.33 31.1509 37.15034+ ।२०।।33 -36.334 35.33 <3.1505 -15) -5.173x + फु२०.133 = 1.5x36.33x 31.1505 +5.1791 +11.+58 - २५० . Thee no of hole of Ex = 21.40 1095- anoon+4 - २१.५फ 57.536) 10 1033 210.२५ 10.25