Question

Which equation obeys the law of conservation of mass? H2(g) O2(g) → H2O(g) H2(g) O2(g) → H2O(g) 4He(g) 2H2(g) O2(g) → 2H2O(g) H2(g) → H2O(g) H2(g) O2(g) → 2H2O(g).

Answer 1

The reaction that follows the law of conservation of mass is $\rm 2\;H_2\;+\;O_2\;\rightarrow\;2\;H_2O$. Thus, option C is correct.

The law of conservation of mass has been stating that in a chemical reaction, the mass at the product and reactants has been equal.

The atoms has been conserved in the reaction that follows the law of conservation of mass.

The moles of reactants and products in the following reactions has been:

A. $\rm H_2\;+\;O_2\;\rightarrow\;H_2O$

Hydrogen: The atoms in reactant=2

Atoms in product=2

Oxygen: The atoms in reactant=2

Atoms in product=1

The product and reactant are not equivalent, thus it not follows the law of conservation of mass.

B. $\rm H_2\;+\;O_2\;\rightarrow\;H_2O\;+\;4\;He$

Hydrogen: The atoms in reactant=2

Atoms in product=2

Oxygen: The atoms in reactant=2

Atoms in product=1

He: The atoms in reactant=0

Atoms in product=4

The product and reactant are not equivalent, thus it not follows the law of conservation of mass.

C. $\rm 2\;H_2\;+\;O_2\;\rightarrow\;2\;H_2O$

Hydrogen: The atoms in reactant=4

Atoms in product=4

Oxygen: The atoms in reactant=2

Atoms in product=2

The product and reactant are equivalent, thus it follows the law of conservation of mass.

D. $\rm \;H_2\;+\;O_2\;\rightarrow\;2\;H_2O$

Hydrogen: The atoms in reactant=2

Atoms in product=4

Oxygen: The atoms in reactant=2

Atoms in product=2

The product and reactant are not equivalent, thus it not follows the law of conservation of mass.

The reaction that follows the law of conservation of mass is $\rm 2\;H_2\;+\;O_2\;\rightarrow\;2\;H_2O$. Thus, option C is correct.

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