What gas is formed when metals react with acids?

Answer 1

Hydrogen.

Remember the general eq'n

Acid + Metal = Salt + Hydrogen

Also

Acid + Base = Salt + Water

Acid + Alkali = Salt + Water

Acid + Carbonate = Salt + Water + Carbon Dioxide.

An example

Zinc and hydrochloric acid

Zn(s) + 2HCl(aq) = ZnCl2(aq) + H2(g) .

Answer 2

In general, we see hydrogen gas liberated when an acid reacts with metal. As just a single example, let's look at hydrochloric acid and sodium. 2HCl + 2Na → 2NaCl + H2 We've made table salt and hydrogen gas by combining these two dangerous chemicals in a very carefully controlled reaction to get our end products. This is true of almost all acids, although you can get a different gas when you use nitric acid. Nitric acid uses the nitrate to oxidize the metal, creating NO2(g) at moderate pH's and NO(g) at lower pH's. Moderate pH: Cu + 4 H+ + 2 NO3- → Cu2+ + 2 NO2 + 2 H2O Low pH: Cu + 4 H+ + NO3- → Cu2+ + 2 NO + 2 H2O Aqua regia, one of the strongest acids you can make, is simply a 3:1 ratio of HCl and HNO3, giving you the 4:1 H+ to NO3- ratio that the low pH reaction requires.