What is the product of the following single replacement reaction Zn 2HCl → ________

The products of the single replacement reaction Zn + 2HCl → are zinc chloride (ZnCl2) and hydrogen gas (H2), giving the complete balanced equation: Zn + 2HCl → ZnCl2 + H2. In this reaction, zinc metal displaces hydrogen from hydrochloric acid because zinc is more reactive than hydrogen on the metal activity series. The zinc atoms lose electrons to form Zn2+ ions that combine with chloride ions to form zinc chloride, while the H+ ions from the acid gain electrons to form H2 gas.

This reaction is commonly performed in chemistry labs and is accompanied by visible signs: when zinc metal (often in the form of granules or strips) is added to hydrochloric acid, vigorous bubbling occurs as hydrogen gas is released, and the solution becomes warm due to the exothermic nature of the reaction. The hydrogen gas produced can be collected and tested with a "pop test"—bringing a lit splint near the gas produces a distinctive popping sound when the hydrogen ignites. This reaction demonstrates the classic pattern of an active metal reacting with an acid to produce a salt and hydrogen gas, following the general form: metal + acid → salt + hydrogen. The need for a coefficient of 2 before HCl comes from balancing the charges: one Zn2+ ion requires two Cl- ions to form neutral ZnCl2.