The equation that has been following the law of conservation has been [tex]\rm H_2\;+\;Cl_2\;\rightarrow\;2\;HCl[/tex]. Thus, option D is correct.
The law of conservation of mass states that in a chemical equation, the atoms of reactants and atoms of products for each elements are equal.
In the given reactions,
A. [tex]\rm H_2\;+\;Cl_2\;\rightarrow\;HCl[/tex]
The equation has 2 atoms of hydrogen and chlorine at reactant side, while 1 atom on product side. Thus, the equation does not follow the law of conservation.
B. [tex]\rm H_2\;+\;O_2\;\rightarrow\;H_2O[/tex]
The equation has 2 atoms of hydrogen and oxygen at reactant side, while 1 atom on product side. Thus, the equation does not follow the law of conservation.
C. [tex]\rm H_2\;+\;O_2\;\rightarrow\;2\;H_2O[/tex]
The equation has 2 atoms of hydrogen and oxygen at reactant side, while 2 atoms of oxygen and 4 atoms of hydrogen on product side. Since, the equation has imbalanced hydrogen it does not follow the law of conservation.
D. [tex]\rm H_2\;+\;Cl_2\;\rightarrow\;2\;HCl[/tex]
The reaction has 2 atoms of hydrogen and chlorine at reactant side, and 2 atom of each on product side. Thus, the equation does follow the law of conservation.
The equation that has been following the law of conservation has been [tex]\rm H_2\;+\;Cl_2\;\rightarrow\;2\;HCl[/tex]. Thus, option D is correct.
For more information about the conservation of mass, refer to the link:
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