1. Determine whether or not the equation below is balanced. If it isn't balanced, write the balanced
form. Also, identify the reactant(s) and product(s) in this equation. Finally, label this as one of the
five types of reactions: combination, decomposition, substitution, double replacement, or
reversible.
Zn
+
HCI
→
ZnCl2
+
H2

A good answer should contain the following:

1. The equation isn't balanced because there aren't equal numbers of hydrogen or chlorine atoms on both sides of the equation. To correct this, a coefficient of 2 must be placed in front of HCl on the left-hand side of the equation.

Zn+2HCl→ZnCl2+H2

Zn and 2HCl are the reactants; ZnCl2 and H2 are the products. This is a substitution reaction because a free element (Zn) replaces another element (H) in a compound.

2. This is a balanced equation because the same types of atoms and the same numbers of each atom are present on both sides of the equation. 8 S atoms are found on both sides of the equation, and 48 F atoms are found on both sides of the equation. S8 and 24F2 are the reactants; 8SF6 is the product. This is a combination reaction because two substances (S8 and 24F2) undergo a chemical union to form a more complex substance (8SF6).

S8+24F2→8SF6

3. In ferric oxide (Fe3O4), there are 3 atoms of iron (Fe) and 4 atoms of oxygen (O). From the Periodic Table of Elements, we know that the atomic mass of iron is 55.8457 and the atomic mass of oxygen is 15.9994.

Fe3 = 55.8457 × 3 = 167.5371

O4 = 15.9994 × 4 = 63.9976

167.5371 + 63.9976 = 231.5347 (231.535 rounded)

Therefore, the molecular mass of ferric oxide is 231.535.

4. The percentage composition of chlorine in CaCl2 is derived as follows:

The molecular mass of the entire compound is:

Ca = 40.078 × 1 = 40.078

Cl2 = 35.4527 × 2 = 70.9054

40.078 + 70.9054 = 110.9834 (110.983 rounded)

The atomic mass of each element (or its multiple) is divided by the molecular mass of the compound:

Ca = 40.078 ÷ 110.983 = 0.361

Cl2 = 70.9054 ÷ 110.983 = 0.639

Multiplying each by 100 will turn these into percents. Therefore, the percentage composition of chlorine is 63.9%.

5. i. a, c, f, h

ii. e

iii. b, d, g, i

iv. i

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