a 6 g sample of magnesium was burned in a crucible producing 10 g of magnesium oxide. What mass of oxygen reacted with magnesium to form the 10 g of magnesium oxide?
2Mg + O2 ==> 2MgO
mols MgO = grams/molar mass = approx 0.25 but you need a more accurate answer.
Then convert mols MgO to mols O2 using the coefficients in the balanced equation. That is 0.25 mols MgO x (1 mol O2/2 mols MgO) = 0.25 x 1/2 = 0.125 mols O2.
g O2 = mols O2 x molar mass O2 = ?
IF you knew that all of the 6g Mg starting material was consumed, then you could have used the law of Conservation of mass or
6g Mg + ?g O2 = 10 g and g O2 = 4 grams.
To find the mass of oxygen that reacted with magnesium to form the magnesium oxide, we first need to determine the mass of magnesium that reacted.
Given that the initial mass of magnesium was 6 g and the final mass of magnesium oxide was 10 g, we can calculate the mass of magnesium that reacted by subtracting the final mass of magnesium oxide from the initial mass of magnesium:
Mass of magnesium reacted = Final mass of magnesium oxide - Initial mass of magnesium
= 10 g - 6 g
= 4 g
Now that we know that 4 g of magnesium reacted, we can consider the balanced chemical equation for the reaction of magnesium with oxygen:
2 Mg + O2 -> 2 MgO
The balanced equation tells us that 2 moles of magnesium react with 1 mole of oxygen to form 2 moles of magnesium oxide.
To find the mass of oxygen that reacted with the 4 g of magnesium, we need to convert the mass of magnesium to moles using its molar mass, and then use the stoichiometry of the balanced equation to determine the moles of oxygen.
The molar mass of magnesium is 24.31 g/mol.
Moles of magnesium reacted = Mass of magnesium reacted / Molar mass of magnesium
= 4 g / 24.31 g/mol
≈ 0.1645 mol
According to the stoichiometry of the balanced equation, 2 moles of magnesium react with 1 mole of oxygen. Therefore, the moles of oxygen that reacted would be half the moles of magnesium reacted:
Moles of oxygen reacted = Moles of magnesium reacted / 2
= 0.1645 mol / 2
= 0.08225 mol
Finally, we can convert the moles of oxygen reacted to mass using the molar mass of oxygen, which is 16 g/mol:
Mass of oxygen reacted = Moles of oxygen reacted x Molar mass of oxygen
= 0.08225 mol x 16 g/mol
≈ 1.316 g
Therefore, approximately 1.316 grams of oxygen reacted with the magnesium to form the 10 grams of magnesium oxide.