Write balanced molecular and net ionic equations for the reactions of (c) hydrobromic acid with magnesium
In this equation, we're dealing with magnesium solid being dissolved in hydrobromic acid. So we have to look to see is magnesium above hydrogen? If so it can displace hydrogen from HBR to produce H2 gas. So magnesium is right here, it is above hydrogen therefore it will be able to displace hydrogen from the acid. So remember magnesium is in group 2A so it's plus 2, bromide ion is in group 7A so it's -1. The numbers are different so we criss-cross them to write the product. Plus H2 gas as a product.
Now remember, for the total or complete ionic equation we break up only aqueous compounds. So we have magnesium solid plus 2 H+ aqueous plus 2 BR- aqueous produces MG2+ aqueous plus 2 bromide ions aqueous plus H2 gas. So we're going to say we're going to get rid of spectator ions, the spectator ions here are bromide ions. Everything else comes down to give us our net ion equation. So we have magnesium solid plus 2 H+ aqueous gives us MG2+ aqueous plus H2 gas. So remember, you can find the same type of activity series chart within the chapter. We use it in reference of the metal towards the acid to figure out can we displace hydrogen gas or not?