Mohr's salt is a pale green crystalline solid which is soluble in water. It is a 'double sulfate' which contains two cations, one of which is Fe2+.The identity of the second cation was determined by heating solid mohr's salt with solid sodium hydroxide and a colourless gas was evolved. The gas readily dissolved in watdr giving an alkaline solution. A grey green solid residue was also formed which wasd insoluble in water. Whate are the identities of the gas and solid residue?
A. Gas: H2 Residue: FeSO4
B.NH3 Na2SO4
C. NH3 Fe(OH)2
D. SO2 Fe(OH)2

Question

Mohr's salt is a pale green crystalline solid which is soluble in water. It is a 'double sulfate' which contains two cations, one of which is Fe2+.The identity of the second cation was determined by heating solid mohr's salt with solid sodium hydroxide and a colourless gas was evolved. The gas readily dissolved in watdr giving an alkaline solution. A grey green solid residue was also formed which wasd insoluble in water. Whate are the identities  of the gas and solid residue? 
A. Gas: H2 Residue: FeSO4
B.NH3     Na2SO4
C. NH3    Fe(OH)2
D. SO2    Fe(OH)2

anonymous · Answer

Use the properties given to narrow it down.  

The gas readily dissolves in water. NH3 and SO2 are water soluble. Of these, NH3 is the most soluble in water.

The gas dissolves in water to produce an alkaline solution. This eliminates SO2, which forms an acid in water. NH3 forms a base when dissolved in water to form ammonium hydroxide, NH4OH. So the best choices are b and c. 

A grey-green solid is formed which is insoluble in water. Look at choices b and c carefully. In choice b you have sodium sulfate, which does not have these properties, but ferrous hydroxide does.

anonymous · Answer

Ohhhh!! so hydrogen is not soluble in water?

anonymous · Answer

Oh i got it hydrogen is nonpolar while water is polar. thank you so much you really are a life saver!