If 1.0 liter of solution is to be made of a 0.010 M in Mg(NO3)2 and 0.10 M in aqueous ammonia, how many moles of NH4Cl are necessary to prevent the precipitation of magnesium hydroxide (neglect change in volume due to addition of NH4Cl)? The solubility product for Mg(OH)2 is 1.5× 10-11, and the Kb for ammonia is 1.8 × 10-5.