Question

How do I balance this redox equation using the oxidation-number-change method?

Answer 1

@justuu @dan815

Answer 2

\(HCl(aq)+Zn(s)->ZnCl_2(s)+H_2(g)\)

Answer 3

@Preetha

Answer 4

@TheSmartOne @zepdrix

Answer 5

@Joel_the_boss

Answer 6

split the reaction into its two half-reactions

Answer 7

Yay, you're back on!

Answer 8

zinc gets oxidized, and the hydrogen ion gets reduced

Answer 9

How do I do that?

Answer 10

Do you see how the zinc starts with a charge of zero and ends with a charge of +2?

Answer 11

Yes

Answer 12

so the half-reaction for the zinc is\[Zn^0 \rightarrow Zn^{+2} + 2e^{-1}\]

Answer 13

How/Why?

Answer 14

because the only way for a zinc to form a +2 charge from a zero charge is to lose 2 electrons

Answer 15

oh, okay.

Answer 16

what happens to the \(hydrogen\) in the reaction?

Answer 17

it starts with +1, correct?

Answer 18

it does, and how does it end as a product?

Answer 19

to be honest, I'm not sure...

Answer 20

when it's bonded to itself, a diatomic molecule like hydrogen has a charge of zero

Answer 21

Oh, okay.

Answer 22

so does \(O_2\), \(N_2\), and all monatomic solids like \(Zn\), \(Fe\), and \(C\) all have charges of zero

Answer 23

since the hydrogen starts as +1 and ends as a 0, what is its half-reaction?

Answer 24

\(H^{1+}+e^{-1} ->H^0\)?

Answer 25

close, but the product is still \(H_2\), so you need more than 1 \(H^{+1}\) ion

Answer 26

\[2H^{+1} + 2e^{-1} \rightarrow H_2\]

Answer 27

Oh, okay.

Answer 28

so how does this balance it?

Answer 29

each half-reaction is separate, but if you add them together, like you could add 2 algebraic equations together, watch what happens

Answer 30

and it's balanced?

Answer 31

it is, and see how one half-reaction produce 2 electrons, and the other half-reaction uses 2 electrons as a reactant?

Answer 32

so the electrons cancel on both sides because they're like terms\[Zn^0 + 2H^{+1} + \cancel{2e^{-1}} \rightarrow Zn^{+2} + H_2 + \cancel{2e^{-1}}\]

Answer 33

Oh, wow, thank you! it actually makes sense now.

Answer 34

YW

Answer 35

Do you think you might be able to help me more if I need it? I don't think I will.

Answer 36

if i'm available, i'll see what i can do

Answer 37

all redox reactions can get balanced this way, you split the reaction into its two halfs, balance each half separately, then add them back together

Answer 38

Thank you so much! I used to love chem...and now.. not so much XD and okay, thank you