How many molecules are in 4 grams of MgCI2?

What are the choices?

Idont know. if you want an answer you need to give us some context dude.

They make up examples of physical properties 

  the volume of  0.220 m k2s    solution  required  to  completely  react with 175 ml  of 0.115m co(no3)2  calculate the moles  of co(no3)2 =  molarity x volume/1000175 x0.115/1000= 0.02  moleswrite  the reacting  equationk2s(aq)  +  co(no3)2  = 2 kno3(aq)  + cos(s)by  use  of mole ratio between k2s to co(no3)2 which  is  1: 1 the moles of k2s is therefore = 175  x0.115/1000= 0.02  molesvolume = moles/molarity=0.02/0.22=0.09  ml  of k2s