Question

The chemical equation below shows the burning of magnesium with oxygen to form magnesium oxide 2Mg + 02 --> 2MgO the molar mass of O2 is 32.0g/mol. what mass, in grams, of O2, is required to react completely with 4.00 mol of Mg? a. 2.00 b. 64.0 c. 128 d. 256

Answer 1

B.) 2Mg + 02 --> 2MgO. According to stoichiometry, 2 moles of Mg reacts with 1 mole of O2. Therefore 4 moles of Mg will react with 2 moles of O2. Therefore mass of O2 required = moles of O2 x molar mass of O2 = 2 x 32 = 64 grams.

Answer 2

The required mass of oxygen to react with 4 moles of Mg is 64 grams

Step-by-step explanation:

You know the reaction where magnesium is burned with oxygen to form magnesium oxide:

2Mg +
`O_(2)` --> 2MgO

Oxygen is required to react completely (that is, sufficient oxygen must be present for the reaction to occur) with 4 moles of Mg. For that you observe the stoichiometry of the reaction, the amount of reagents needed. Stoichiometry in this case tells you that in order for 2 moles of Mg to react, you need 1 mole of
`O_(2)`. Taking this into account, you apply a rule of three: if to react with two moles of Mg you need 1 mole of
`O_(2)`, how many moles of
`O_(2)` do you need to react with 4 moles of Mg?

`moles of O_(2) =(4 molesMg*1molO_(2) )/(2 molesMg)`

moles of O_{2} =2 moles

To know the mass of
`O_(2)` that reacts, you must take into account the molar mass of oxygen, which is 32 grams / mol and you can apply another rule of three: if in a mole of
`O_(2)` there are 32 grams, how many grams are in 2 moles of oxygen?

`mass of oxygen=(2 moles* 32 grams)/(1mol)`

mass of oxygen= 64 grams

Then, the required mass of oxygen to react with 4 moles of Mg is 64 grams