Answer:
1) D; 2) B
Explanation:
1) Conservation of atoms
D is correct.
It has four atoms of H and two of O on each side of the reaction arrow.
A. Wrong. It has the same number of H and O on each side, but it has the wrong product. The reaction forms O₂ molecules, not O atoms.
B. Wrong. Atoms are balanced, but the products are incorrect.
C. Wrong. Atoms are balanced, but the reactants are incorrect.
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2) Chemical equations
B is correct.
The atoms are balanced, and the equation shows the correct formulas of the molecules.
A. Wrong. Atoms are balanced, and the formulas are correct, but the equation is not in its simplest form. The coefficients are not in their lowest terms. We must divide every coefficient by six to get the correct equation: H₂ + Cl₂ ⟶ 2HCl.
C. Wrong. The reactants are incorrect, and the equation is not in its lowest terms.
D. Wrong. The reactants are incorrect.