A. Zinc metal (Zn), since it loses electrons to form the Zn²⁺ ion
15.
A combustion reaction is best defined as a chemical reaction in which a substance reacts (typically rapidly) with oxygen, releasing energy primarily in the form of:
A.
Heat and light
B.
Only electrical energy, with no accompanying release of heat or light whatsoever
C.
Only mechanical (kinetic) energy, with no accompanying release of heat or light whatsoever
D.
Only sound, with no accompanying release of heat or light whatsoever
When combustion occurs with an INSUFFICIENT (limited) supply of oxygen, this is termed 'incomplete combustion', and it characteristically produces which additional, potentially hazardous product, in place of (or alongside) carbon dioxide?
A.
Carbon monoxide (CO), a toxic gas, along with soot (unburnt carbon particles)
B.
Nitrogen gas (N₂), in greater quantity than during complete combustion
C.
Pure oxygen gas (O₂), in greater quantity than during complete combustion
D.
An increased yield of pure water (H₂O), with no other notable by-products
A. Carbon monoxide (CO), a toxic gas, along with soot (unburnt carbon particles)
18.
Combustion reactions, particularly those involving fossil fuels such as coal and petroleum, are a significant contributor to environmental air pollution primarily through the release of which group of harmful gases?
A.
Helium gas and neon gas exclusively, both of which are chemically inert noble gases
B.
Pure water vapour (H₂O) exclusively, with absolutely no other gaseous by-products
