Question

How many grams of mgo are produced when 40.0 grams of o2 react completely with mg? 2 mg (s) + o2 (g) → 2 mgo (s)?

Answer 1

Answer: -

100 grams

Explanation: -

Mass of Oxygen = 40 g

Chemical formula of oxygen gas = O2

Molar mass of oxygen = 16 x 2 = 32 gram

Atomic mass of Mg = 24g

Molar mass of MgO = 24 x 1 + 16 x 1 =40 gram

The balanced chemical equation for the reaction is

2Mg + O2 -- > 2 MgO

So from the balanced equation we see that 1 O2 react to give 2 MgO

32 grams of O2 react to give 2 x 40 gram of MgO

40 grams of O2 react to give $\frac{2 x 40 gram x 40 gram}{32 gram}$

=100 gram of MgO

Answer 2

Magnesium is a chemical element, which have molar mass of 15 u. It reacts with oxygen to form magnesium oxide, MgO. The molar mass of oxygen is 16 u. The number of grams of MgO produced will be 100 grams.

Given that,

• Given Mass of oxygen= 40 g
• Molar Mass of Oxygen = 16 g
• Mass of Magnesium = 24 g
• Molar Mass of Magnesium Oxide = 24 + 16 = 40 g

Now, the balanced chemical equation between magnesium and oxygen is:

• $\text{2 Mg + O}_{2}\rightarrow \;\text {2 MgO}$

Stoichiometrically, in the reaction,  1 molecule of oxygen gives 2 MgO.

As in the reaction:

• O$_2$ = 16 X 2 = 32 g/mol
• MgO = y grams.

40 g of Oxygen react to give:

• $\dfrac{2\times 40\times 40 }{32}&=100 \;\text g$

Therefore, 100 g of MgO will be produced when 40 g of Oxygen reacts with Magnesium.

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