Answer: The given quantity is 2 moles of magnesium or 48 g of magnesium.
The unknown quantity is mass of MgO in grams.
Molar mass of MgO = 40 g
Explanation: [tex]2Mg+O_2\rightarrow 2MgO[/tex]
As can be seen from the chemical equation, 2 moles of magnesium react with 1 mole of oxygen gas to give 2 moles of MgO.
According to mole concept, 1 mole of every substance weighs equal to its molar mass.
Thus [tex]2\times 24= 48 g[/tex] of magnesium produce=[tex]2\times 40= 80 g[/tex] of MgO.
Molar mass is the mass in grams of 1 mole of the substance.
Thus if 2 moles of MgO weigh= 80 g
1 mole of MgO will weigh=[tex]\frac{80}{2}\times 1 =40g[/tex]
Thus molar mass of MgO is 40 g.
