# 1 gm of magnesium is burnt with 0.56gm of O2 in a closed vessel. Which reactant is left in excess and how much?

By BYJU'S Exam Prep

Updated on: September 25th, 2023

Magnesium is in excess and by 0.16.

(At. wt. Mg = 24 ; O2 = 16)

The equation can be written as:

2Mg + O2 → 2MgO

(s) (g) (s)

Therefore, in order to make 2 moles of MgO, 1 mole of O2 is needed.

Now we have to calculate the actual moles.

We know that

moles= mass/ molar mass

Mg= 1/24 = 0.041667

O2 = 0.56/32 = 0.0175

Finding their ratio

Mole ratio of Mg: O2 = 2:1

Now we have to find mass of Mg that reacts:

it implies that 2 moles of Mg and 1 mole of O2 react.

If 1 = 2

Then 0.0175 = 0.0175 x 2

= 0.035 moles of magnesium

mass of magnesium that reacts:

mass = moles x molar mass

Substituting the values we get

= 24 x 0.035

= 0.84 g

Accordingly, just 0.84 grams of the magnesium’s 1 gram reaction weight is utilised.

As a result, magnesium is overexposed and by 0.16

### Uses of Magnesium

• Scientists use magnesium in medicine. It is commonly used to treat issues with the skin, attention deficit hyperactivity disorder (ADHD), anxiety, mania, post-operative recuperation, etc.
• A great source of magnesium is the green leafy vegetable. Magnesium is also abundant in whole grains, seeds, and nuts, particularly almonds.
• Magnesium is also present in the flashbulbs. Mg burns brightly, making it possible for photographers to shoot pictures in low light.

Summary:-

## 1 gm of Magnesium is burnt with 0.56gm of O2 in a closed vessel. Which reactant is left in excess and how much?

1 gm of magnesium is burnt with 0.56gm of O2 in a closed vessel. Magnesium is in excess and by 0.16.

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