Suggest why cao rather than mgo is used to dry ammonia.

Ca2+ is less electro-positive than Mg2+. Therefore, CaO is less ionic than MgO. and in turn means that the O in CaO is more like O2– will react with H in H2O more so than O2- of MgO, because it is more ionic means O is strongly bonded to Mg compare to Ca

So what you would do is go through and add 3 teaspoons(tsp) 6 times because of the 6 tablespoons(tbsp). which will give you an answer of 18. another way is to multiply 3x6=18.