Question

Magnesium nitrate, Mg(NO3)2, will decompose when heated to give a white solid and a mixture of
gases. One of the gases released is an oxide of nitrogen, X.
7.4g of anhydrous magnesium nitrate is heated until no further reaction takes place.
What mass of X is produced?
B 2.3g
C 3.05
D 4.6g​

Answer 1

Mass of X produced : D. 4.6 g

Further explanation

Reaction

Decomposition of Magnesium nitrate into Magnesium oxide, Oxygen, and Nitrogen oxides

2 Mg(NO₃)₂ → 2 MgO + 4 NO₂ + O₂

mol Magnesium nitrate-Mg(NO₃)₂(MW=148,3 g/mol) :

$\tt \dfrac{7.4}{148.3}=0.05$

mol ratio Mg(NO₃)₂ : NO₂ = 2 : 4, so mol  NO₂ :

$\tt \dfrac{4}{2}\times 0.05=0.1$

mass NO₂(MW=46 g/mol) :

$\tt 0.1\times 46~g/mol=4.6~g$

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