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Solution: Write balanced molecular and net ionic equations for the rea...


Write balanced molecular and net ionic equations for the reactions of (a) manganese with dilute sulfuric acid

Video Transcript

Hey guys, here we need to write the molecular and net ionic equation when we have manganese with sulphuric acid. So here manganese will be in its natural form, so it's manganese, solid, plus sulphuric acid, which will be aqueous. Now for us to be able to tell what the products will be, we have to consult our activity series chart. So, this is our activity series chart, and they're saying sulphuric acid has in it H+. So really what we're looking at is this part here, hydrogen. So we have hydrogen there, and we're going to say we're dealing with manganese. Manganese happens to be a metal above it. So basically if you're an element above hydrogen, you can displace hydrogen from the acid to produce H2 gas. So here, let's just take a look at this. We're going to say from lithium down to sodium, they can react with water to form H2 gas, from lithium down to iron, here, they react with steam to form H2 gas, and then from lithium all the way down to lead, they can react with acids to form H2 gas.

Now, metals below hydrogen will not dissolve in acids so they will not produce H2 gas. So that's how we look at this activity series chart. This chart can be found within the chapter, and you need it to be able to answer this question. So again, manganese is above hydrogen so it can react with acids to form H2 gas. That's what we can say there. So, come back up here, manganese here will be manganese 2+ with sulphate ion, which is 2-, they just combine and their charges cancel out. So we would have MnSO4, here it would be aqueous because of the solubility rules, we produce hydrogen gas. So that there represents our balanced equation. Now they're asking us to give them the net ionic equation, so right now this is just our molecular equation.

Next what we're going to do is we're going to break it down to the total, or complete, ionic equation. Remember, in this we only break up aqueous things, so here Mn, solid, plus two H+ ions, which breaks up because it's aqueous, plus SO4 2- aqueous, gives us Mn 2+ aqueous plus SO4 2- aqueous plus H2 gas. Now remember when we're going here we're doing the net ionic equation now. And remember for the net ionic equation we ignore spectator ions, ions that look the same on both sides of the equation. Alright, so that is not a spectator, because Mn 2+ is not on both sides. The spectator ion looks like it's the sulphate ion. So, those don't come down there, but everything else does. So my net ionic equation would be this. So again, to be able to do this correctly we need to have our activity series chart handy. We look at it in order to see what the position of the metal is, if it's above hydrogen, it can displace it to make H2 gas. If it's below it, it won't work.

This is an example of a hydrogen displacement equation. Displacement means we're producing H2. We could also say that this is an example of a single replacement, or single replacement reaction, where one element kicks out another element. In this case it was the manganese coming in and kicking out the hydrogen. So now the manganese is with sulphate and hydrogen is all here by itself.