## Writing half reactions

melissa_dis4K
Posts: 106
Joined: Fri Sep 28, 2018 12:28 am

### Writing half reactions

When given a question like the one attached, where the given reactions have H+ like part c, how do I know on which equation to write the H+ on when doing the half reactions?
Attachments

Brian Chhoy 4I
Posts: 66
Joined: Fri Sep 28, 2018 12:16 am

### Re: Writing half reactions

The H+ will be with the Cr207 because the h20 will be included with this half reaction to balance the oxygens, and the H+ will be needed the balance the hydrogens from the h20.

hanna_maillard3B
Posts: 61
Joined: Fri Sep 28, 2018 12:23 am

### Re: Writing half reactions

When a molecule consists of an oxygen atom/s and changes (becomes product / or is reversed into reactant) into its elemental form (i.e. MnO4- becomes Mn2+), you must accommodate for the missing oxygen atom/s. Therefore, when the reaction occurs in an acidic solution, you add H2O to the side without the oxygen and add H+ to the side with the oxygen (to balance the new H atoms from the addition of water). So for this question, you keep the H+ ions with the Cr2O7(2-) because that will be the reaction that requires additional O atoms to balance it.

Aili Ye 4L
Posts: 58
Joined: Fri Sep 28, 2018 12:16 am

### Re: Writing half reactions

The H+ would be with the Cr2O7 since the oxygen atoms in it are balanced with H20, and the H20 are balanced with H+

marisaimbroane1J
Posts: 69
Joined: Fri Sep 28, 2018 12:23 am

### Re: Writing half reactions

It will end up depending on which half reaction requires the H+. You need to balance both half reactions and know that you should end up with (in that example) 8H+ on the left side of the equation.

Niveda_B_3I
Posts: 60
Joined: Fri Sep 28, 2018 12:24 am

### Re: Writing half reactions

The H+ would be with the Cr2O7 since the oxygen atoms in it are balanced with H20, and the H20 are balanced with H+

Calvin Patel 2H
Posts: 37
Joined: Fri Sep 28, 2018 12:22 am

### Re: Writing half reactions

You would put the H+ with the Cr2O7 since the oxygen atoms are balanced with H20, and the H20 is balanced with the H+

Abby-Hile-1F
Posts: 46
Joined: Fri Sep 28, 2018 12:16 am

### Re: Writing half reactions

since oxygen atoms are balanced with H20, you have to then balance the H20 with H+. Because of this, you would put the H+ with the Cr2O7