Question

1) Students set up the apparatus you see here to separate water into its two components: hydrogen and oxygen. The illustration also shows us that hydrogen and oxygen, when uncombined, exist as diatomic molecules. Based on the chemical formula of water, H2O. we would expect twice as many hydrogen bubbles to collect on the negative electrode compared to the number of oxygen bubbles collecting on the positive electrode. Which chemical equation best illustrates how the total number of atoms is conserved during this chemical reaction.
A) 2H2O ⇒ 2H2 + 2O
B) H2O ⇒ 2H + O
C) H2O ⇒ H2 + O2
D) 2H2O ⇒ 2H2 + O2

2) A synthesis reaction combines two or more elements to form a compound. In this case, hydrogen and chlorine have combined to hydrochloric acid or hydrogen chloride. Which equation correctly represents this chemical reaction?
A) 6H2 + 6Cl2 ⇒ 12HCl
B) H2 + Cl2 ⇒ 2HCl
C) 2H + 2Cl ⇒ 2HCl
D) H + Cl ⇒ HCl

2nd image goes with number 2

Answer 1

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.