it is an acid because it increases the concentration of hydronium ions.
hcl is an acid. when hcl is added into water, it undergoes the following dissociation:
hcl + h₂o(l) → h₃o⁺(aq) + cl⁻(aq).
the arrhenius definition defines acids as subtances that release h⁺(aq) when put in water. this h⁺(aq) ions that hcl releases reacts with water to form h₃o (hydronium), leading to an increase in concentration of h₃o.
the correct answer is a compound since heterogeneous means multiple of the same different elements and substance isnt accurate and homogeneous means same. so the correct answer is a
hmmmm let me think about that