Question

1. in single - replacement reactions, a single element replaces a similar element in a compound.

in this generalized reaction, a metal replaces a metal:
ab + c→cb + a
a nonmetal can also replace a nonmetal:
ab + d→ad + b
in both generalized reactions, the compounds are typically aqueous. this means the compounds are dissolved in water.
describe what the circles and squares represent in the generalized reactions.
i need a hint
circles represent metals.
squares represent nonmetals.
circles represent nonmetals.
squares represent metals.

Explanation:

In single - replacement reactions shown, the circles and squares are placeholders for elements. In the metal - replacement reaction, a metal (C) replaces a metal (A) in the compound AB. In the non - metal replacement reaction, a non - metal (D) replaces a non - metal (B) in the compound AB. So, circles represent elements (either metal or non - metal) and squares represent compounds.

Answer:

Circles represent elements. Squares represent compounds.