Answer:
a) 2Cu(s) + S(s) → Cu₂S(s)
b) 2SO₂(g) + O₂(g) → 2SO₃(g)
c) 4HCl(aq) + MnO₂(s) → MnCl₂(aq) + 2H₂O(l) + Cl₂(g)
d) C₆H₆(l) + 15/2 O₂(g) → 6CO₂(g) + 3H₂O(l)
Explanation:
First, we have to write the chemical formulas for reactants and products. Then, to identify which is the state of matter of each compound (liquid: l, solid: s, aqueous: aq, gas: g). Finally, we write the equation and balance the atoms.
a) Solid copper reacts with solid sulfur to form solid copper(I) sulfide.
Reactants: solid copper (Cu(s)) and solid sulfur (S(s)). Product: copper(I) sulfide (Cu₂S) because sulfur anion has two negative charges (S⁻²) and we need two copper ions with one positive charge (Cu⁺) to obtain the neutral compound.
The balanced requires a coefficient of 2 for Cu(s) to balance the 2 Cu atoms on the products side:
2Cu(s) + S(s) → Cu₂S(s)
(b) Sulfur dioxide gas reacts with oxygen gas to form sulfur trioxide gas.
Reactants: sulfur dioxide (SO₂) and oxygen gas (which is a diatomic molecule: O₂). Products: sulfur trioxide gas (SO₃(s)).
The balanced equation is:
2SO₂(g) + O₂(g) → 2SO₃(g)
We need a coefficient of 2 for SO₂ and SO₃ to balance O and S atoms.
(c) Aqueous hydrochloric acid reacts with solid manganese(IV) oxide to form aqueous manganese(II) chloride, liquid water, and chlorine gas.
Reactants: aqueous hydrochloric acid (HCl(aq)) and solid manganese (IV) oxide (MnO₂(s), because we need two oxygen anions O²⁻ to neutralize 4 positive charges in Mn IV). Products: aqueous manganese(II) chloride (MnCl₂, because we need two chloride ions Cl⁻ to neutralize two positive charges in Mn(II)), liquid water (H₂O), and chlorine gas (Cl₂, because it is a diatomic molecule).
The balanced chemical equation is:
4HCl(aq) + MnO₂(s) → MnCl₂(aq) + 2H₂O(l) + Cl₂(g)
(d) Liquid benzene (C₆H₆) reacts with gaseous oxygen to form carbon dioxide and liquid water.
Reactants: benzene (C₆H₆) and gaseous oxygen (O₂). Products: carbon dioxide (CO₂, because C has valence IV) and liquid water (H₂O).
The balanced chemical equation is:
C₆H₆(l) + 15/2 O₂(g) → 6CO₂(g) + 3H₂O(l)
In this case, we need a coefficient of 15/2 for O₂ because on the product side there are 15 atoms of O (12 in CO₂ and 3 in H₂O).
