How many grams of magnesium nitride (Mg, N,) are needed to react with an excess amount of potassium oxide to produce 0.5 moles of magnesium oxide (MgO)?​

An atom of sodium-23 (atomic number = 11) has a positive charge of +1. give this information, how many electrons does it have? how many proteins and neutrons does this atom have

How does the motion of particles in a gas change as the gas cools

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