in which type of reaction does a more complex compound break down into two simpler substances?

The type of reaction where a more complex compound breaks down into two or more simpler substances is called a decomposition reaction.

Quick Scoop

• In a decomposition reaction, a single compound (often written as ABABAB) breaks apart into simpler substances (A+BA+BA+B or more).

• It is the opposite of a combination (synthesis) reaction, where simpler substances join to form a more complex compound.

• Example: When calcium carbonate is heated, it decomposes into calcium oxide and carbon dioxide:
  CaCO3→CaO+CO2\text{CaCO}_3\rightarrow \text{CaO}+\text{CO}_2CaCO3​→CaO+CO2​.

So, the answer to: “In which type of reaction does a more complex compound break down into two simpler substances?”
is: Decomposition reaction.

TL;DR: A more complex compound breaking down into simpler substances is undergoing a decomposition reaction.

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