Use the electron-transfer method to balance the equation

Question

Balance the equation involving the reaction of aluminum with hydrochloric acid to produce to aluminum chloride and hydrogen gas.

there's 6 steps in this which is:

1.) Write the skeletal equation

2.) Assign oxidation number

3.) Write the electronic equations for the oxidation and reduction half-reactions

4.) Adjust the coefficients by multiplication

5.) Insert the final coefficients into the skeleton equation

6.) Adjust the coefficients of the non-redox members to balance both sides of the equation

Please show them in this steps, Thank you :)

Answer 1

1) Aluminum + HCl → AlCl₃ + H₂ which is very easy to balance normally, but I guess this is practice.

2) Al and H₂ have OxNo of 0 because they are elements in natural states

H in HCl is +1 (Ox state rule: H is +1 when reacted unless a hydride)

Al in AlCl₃ is usually considered ionic, so Al is +3 as that is the ion it forms. You can also back it out from the sum of the oxidation states for a compound being 0 and the chlorides are -1 unless forced into another state by oxygen or fluorine)

3) Al → Al³⁺ + 3e^-

and 2H⁺ + 2e^- → H₂ note that H must be balanced in 1/2-reaction before electrons balance needs of oxidation number changes. Also HCl is strong and AlCl₃ dissolves - chlorines are spectators

Also, in this simple redox, the electrons are merely balancing charge. That is often not the case.

4) In order for the number of electrons to cancel, you need to double Al equation and triple H equation and add:

5) 2Al + 6H⁺ → 2Al³⁺ + 3H₂

6) There really is no balancing of Cl necessary as it must balance if you associate HCl with H⁺ and AlCl₃ with Al³⁺

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