How to do this net ionic formula equation?

Question

Strontium metal is placed in hydrobromic acid.

Net ionic formula?

Answer is

Sr + H(+) --------> Sr(2+) + H2

Please walk through this problem for me to the answer?

Answer 1

There should be, the answer you have been given is not properly balanced.

To do this first write a balanced chemical equation

Sr(s) + 2HBr(aq) ------> SrBr2(aq) + H2(g)

Now, expand it out to show all the individual species (ie, split the aqueous compounds into their constituent ions)

This is the full ionic equation:

Sr(s) + 2H+(aq) + 2Br-(aq) -------- Sr2+(aq) + 2Br-(aq) + H2(g)

Now, for the net ionic equation you only write down the species in the equation that are changing.

You can see that you have 2Br-(aq) on both sides of the equation. They are not participating in the reaction, so they are left out of the NET ionic equation.

The Sr is going from Sr solid, to a cation in aqueous solution (it is being oxidised - losing electrons) so it must be shown in th NET ionic equation.

The H+ is being reduced (gaining electrons) from aqueous cation to H2 gas, so it must also be in the net ionic equation.

Sr(s) + 2H+(aq) ------> Sr2+(aq) + H2(g)

Answer 2

Because the Sr transfers it's electrons to hydrogen ions. (Sr reduces H+) However, to become a Sr 2+, it needs to lose two electrons. Therefore it'll need 2 H+.