Question

1. choose the best answer.

which type of reaction occurs when two elements come together to form one compound?
synthesis
compound
decomposition
replacement

1. choose the best answer.

another name for synthesis reaction is a ______ reaction.
decomposition
compound
combination
replacement

1. choose the best answer.

which of these reactions does not represent a synthesis reaction?
4al(s) + 3o₂(g) → 2al₂o₃(s)
na₂o + co₂ → na₂co₃
2h₂(g) + o₂(g) → 2h₂o(g)
2kcl(s) → 2k(s) + cl₂(g)

Explanation:

1. A synthesis reaction is defined as two or more reactants combining to form a single product, which matches the description of two elements forming one compound.
2. Synthesis reactions are also known as combination reactions, as multiple substances combine into one.
3. A synthesis reaction has multiple reactants forming one product. The reaction $\text{2KCl}(s)

ightarrow \text{2K}(s) + \text{Cl}_2(g)$ has one reactant forming two products, which is a decomposition reaction, not synthesis.

Answer:

1. A. synthesis
2. C. combination
3. D. $\text{2KCl}(s)

ightarrow \text{2K}(s) + \text{Cl}_2(g)$