Question

in a science demonstration, a teacher mixed zinc (zn) with hydrogen chloride (hcl) in a flask and quickly attached a balloon over the mouth of the flask. bubbles formed in the solution and the balloon inflated.
what most likely occurred during this demonstration?
the zn and hcl both retained their identity.
either zn or hcl, but not both, retained its identity.
evaporation of one of the substances occurred.
one or more new substances formed.

Explanation:

Step1: Analyze the reaction

Zinc (\(Zn\)) reacts with hydrogen chloride (\(HCl\)) in a chemical reaction. The chemical equation for the reaction is \(Zn + 2HCl=ZnCl_{2}+H_{2}\uparrow\).

Step2: Determine the nature of the reaction

In a chemical reaction, new substances are formed. Here, zinc chloride (\(ZnCl_{2}\)) and hydrogen gas (\(H_{2}\)) are new substances. Evaporation is a physical change (not relevant here as it's a chemical reaction). If either \(Zn\) or \(HCl\) retained its identity, it would imply no reaction (but a reaction occurred as bubbles (gas - \(H_{2}\)) formed and balloon inflated). And \(Zn\) and \(HCl\) do not both retain their identity as they react to form new substances.

Answer:

One or more new substances formed.