Video Transcript
Which of the following equations
shows the reaction between zinc metal and hydrochloric acid? (A) Zn solid plus two HCl aqueous
react to produce ZnCl2 aqueous plus H2 gas. (B) Zn solid plus HCl aqueous react
to produce ZnH aqueous plus Cl gas. (C) Zn solid plus HCl aqueous react
to produce ZnCl aqueous plus one-half H2 gas. (D) Zn solid plus two HCl aqueous
react to produce ZnH2 aqueous plus Cl2 gas. Or (E) Zn solid plus two HCl
aqueous react to produce ZnHCl aqueous plus HCl gas.
We are considering the reaction
between zinc, a metal, and hydrochloric acid, an acid. Reacting a metal with an acid
produces a salt and hydrogen. If we look at the products of
options (A) to (E), we can see that only option (A) and option (C) list hydrogen as
a product. For this reason, we can rule out
option (B), option (D), and option (E). To determine whether option (A) or
option (C) is the answer, we need to figure out which salt is produced, ZnCl2 or
ZnCl.
Cl, or chlorine, is in group 17 of
the periodic table, so it has seven outer-shell electrons. It would generally gain one
electron so that it has eight electrons in its outer shell. So chlorine generally forms Cl−
ions. Zn, or zinc, on the other hand has
two valence or outer-shell electrons, so it will generally form Zn2+ ions. Using this information, we can
determine that ZnCl2 is the most likely product, as ZnCl contains Zn1+ ions. Thus, the answer to the question is
option (A), not option (C).
So the equation that shows the
reaction between zinc metal and hydrochloric acid is (A). Zn solid plus two HCl aqueous react
to produce ZnCl2 aqueous plus H2 gas.
