How many moles of oxygen do you need to burn one mole of Mg?

You need 0.5 moles of oxygen to burn one mole of Mg.

Explanation:

The balanced reaction is:

2 Mg + O₂ → 2 MgO

When chemical changes occur, the chemical elements are conserved, so the number of atoms is the same before and after the change. To represent this equality of the number of atoms, the expression is "balanced" or "equalized". That's why you put a two in front of the magnesium formula and a two in front of the magnesium oxide to equal the number of atoms involved in the change. These numbers used are called stoichiometric coefficients. The stoichiometric coefficients allow to establish the molar ratio in which the reactants combine and the products are formed.

By stoichiometry of the reaction (that is, the relationship between the amount of reagents and products in a chemical reaction) the following amounts of each compound participate in the reaction:

Mg: 2 molesO₂: 1 moleMgO: 2 moles

Then you can apply the following rule of three: if by reaction stoichiometry 2 moles of magnesium reacts with , 1 mole of magnesium reacts with how many moles of oxygen?

amount of moles of oxygen= 0.5 moles

You need 0.5 moles of oxygen to burn one mole of Mg.

Sorry i dont understand the question can you rephase it?

Vander waals forces are inter molecular bonds that exist within molecules of the same substance. a water molecule is made up of oxygen and hydrogen atoms which share electrons between each other. the vander waals forces are forces that exist between multitude of different  molecules of water. dipole dipole forces is the type of vander waals force that exist in water. the oxygen atom which is more electronegative pulls the shared electron closer to itself thus generating a partial negative charge while the hydrogen acquire a partial positive charge. these two different charges causes attraction to occur in water molecules.