Question

If a mass of 2.4 g of magnesium is burnt in air, 4.0 gram of magnesium oxide is formed.
a. What kind of reaction is this ?explain your answer
b. What was the mass of oxygen that reacted with the magnesium? explain your answer
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Answer 1

$_{2}$Answer:

a) Combustion reaction

b) 0.8 g

Explanation:

a) Combustion reaction because magnesium is burnt and is reacting with oxygen in the air. (Mg is getting oxidized)

b)  2Mg + O$_{2}$ ----> 2MgO   (no. of moles = given mass/ molar mass)

moles of Mg = 2.4 / 24

=0.1 mol

ratio of moles of Mg : O$_{2}$

 = 2 : 1

moles of oxygen = 0.1 / 2

= 0.05 mol

mass of oxygen = mol * molar mass

                           =0.05* 16

                           = 0.8 grams