Writing half reactions

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

Writing half reactions

Postby melissa_dis4K » Thu Feb 28, 2019 2:51 pm

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
Screenshot 2019-02-28 at 2.49.38 PM.png

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

Re: Writing half reactions

Postby Brian Chhoy 4I » Thu Feb 28, 2019 3:19 pm

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

Postby hanna_maillard3B » Thu Feb 28, 2019 5:19 pm

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

Postby Aili Ye 4L » Sun Mar 03, 2019 10:05 pm

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

Postby marisaimbroane1J » Mon Mar 04, 2019 7:05 pm

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

Postby Niveda_B_3I » Thu Mar 07, 2019 9:54 am

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

Postby Calvin Patel 2H » Thu Mar 07, 2019 11:38 am

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

Postby Abby-Hile-1F » Sun Mar 10, 2019 7:39 pm

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


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