4. Magnesium and oxygen reaction to create 55 grams of magnesium oxide. How many grams of oxygen was used in this chemical reaction?
Mg + O2 → Mgo

Can someone me with questions 12 and 13 plz.

What is the ph of a solution that has a hydrogen ion concentration of 1.0 * 10 -9 m?

Insoluble sulfide compounds are generally black in color. which of the following combinations could yield a black precipitate? check all that apply. na2s(aq)+kcl(aq) li2s(aq)+pb(no3)2(aq) pb(clo3)2(aq)+nano3(aq) agno3(aq)+kcl(aq) k2s(aq)+sn(no3)4(aq)