In a chemical reaction, hydrogen gas (H2) reacts with oxygen gas (O2) to form carbon dioxide (CO2 molecules) and water molecules (H2O), producing heat.

Question

What kind of chemical reaction is this, and why?

Responses

synthesis, because a substance reacts with oxygen to release heat
synthesis, because a substance reacts with oxygen to release heat

combustion, because a substance reacts with oxygen to release heat
combustion, because a substance reacts with oxygen to release heat

tarnishing, because there are the same number of reactants as products
tarnishing, because there are the same number of reactants as products

tarnishing, because the products are carbon dioxide and water

Answer 1

The correct response is:

combustion, because a substance reacts with oxygen to release heat.

This is because the reaction you described involves hydrogen gas (H2) reacting with oxygen gas (O2) to produce water (H2O) and energy in the form of heat, which is characteristic of combustion reactions. However, there's a small correction needed: hydrogen gas burns in the presence of oxygen to form water (H2O), not carbon dioxide (CO2). Therefore, the reaction is indeed combustion, but the products are water (H2O) rather than carbon dioxide (CO2).