Why can't sodium salt be prepared by double decomposition
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Normally, reacting a metal and an aqueous acid will produce a salt and hydrogen gas, as in the case of iron:

Fe(s)+2HCl(aq)⟶FeCl2(aq)+H2(g)

However, you should not use the same method to produce, for example, sodium chloride:

2Na(s)+2HCl(aq)⟶2NaCl(aq)+H2(g)

Determine the  wavelength of light emitted when an electron  in an li2+ ion  makes a transition from an orbital with n  =  6 to an orbital with n  = 5.