Question

what reaction type, or classification, is represented by no. 4? multiple choice.

1. 2 c₆h₆ + 15 o₂ → 12 co₂ + 6 h₂o
2. h₂o + so₃ → h₂so₄
3. 8 al₂s₃ → 8 al + 3 s₈
4. cucl₂ + h₂s → cus + hcl
5. 2 kbr + cl₂ → 2 kcl₂ + br₂
6. 2 nh₃ + h₂so₄ → (nh₄)₂so₄
7. al₂(so₄)₃ + 3 bacl₂ → 3 baso₄ + 2 alcl₃
8. 2 nh₃ → 3 h₂ + n₂
9. 2 c₂h₂ + 5o₂ → 4 co₂ + 2 h₂o
10. 3 ca + fe₂o₃ → 2 fe + 3 cao

this problem can be solved by dimensional analysis as the primary method, formula where permitted, or simple math. using ratio and proportion methods is not allowed. be sure to show the formula on homework and exams.
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synthesis or combination
single displacement
decomposition
combustion
double displacement

Explanation:

Step1: Recall reaction - type definitions

Synthesis: A + B → AB; Single - displacement: A + BC → AC+ B; Decomposition: AB → A + B; Combustion: Hydrocarbon + O₂ → CO₂ + H₂O; Double - displacement: AB+ CD → AD + CB.

Step2: Analyze reaction 4

The reaction 4 is CuCl₂ + H₂S → CuS + HCl. Here, the cations (Cu²⁺ and H⁺) and anions (Cl⁻ and S²⁻) of the two reactants exchange places. This is characteristic of a double - displacement reaction.

Answer:

double displacement