Question

in which type of chemical reaction do two or more substances combine to form one substance?
synthesis
decomposition
single replacement
double replacement

Explanation:

To determine the correct type of chemical reaction, we analyze each option:

• Synthesis reaction: Defined as a reaction where two or more substances (reactants) combine to form a single new substance (product). The general form is \( A + B

ightarrow AB \).

• Decomposition reaction: Involves a single compound breaking down into two or more simpler substances (opposite of synthesis), general form \( AB

ightarrow A + B \).

• Single replacement reaction: One element replaces another in a compound, general form \( A + BC

ightarrow AC + B \).

• Double replacement reaction: Ions in two compounds exchange places to form two new compounds, general form \( AB + CD

ightarrow AD + CB \).

The question describes a reaction where two or more substances combine to form one substance, which matches the definition of a synthesis reaction.

Answer:

A. synthesis