Considering the following equation, what is the number of moles of oxygen gas needed to react with 4.00 mol of mg is

2mg + o2 --> 2mgo

2.0 mol

1.0 mol

6.0 mol

3.0 mol

2moles

Explanation: 2Mg + O2 --> 2MgO

From the equation, 2 moles of Mg required 1mole of O2.

4 moles of Mg will require Xmole of O2. i.e

Xmol of O2 = 4/2 = 2moles

Therefore, 4moles of Mg requires 2moles of O2

if you mean hydrogen and oxygen then water is the product

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.