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### Topic: Oxidizing and Reducing Questions  (Read 45656 times)

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#### entice

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##### Oxidizing and Reducing Questions
« on: November 29, 2009, 02:01:20 AM »
What is the oxidizing agent in the following chemical reactions
1. 2MnO4- + 5H2SO3 -> 2Mn2+ + 5SO42- + 4H+ + 3H2O
2. 5S + 6KNO3 + 2CaCO3 -> 3K2SO4 + 2CaSO4 + CO2 +3N2

What is the reducing agent in the following chemical reaction
1. 5Fe2+(aq) + MnO4-(aq) + 8H+(aq) -> 5Fe3+(aq) + Mn2+(aq) + 4H2O(l)

What element is oxidized in the following chemical reaction
1. NiO2 + Cd + 2H2O -> Ni(OH)2 + Cd(OH)2

An explanation would be greatly appreciated. Thanks

#### pear

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##### Re: Oxidizing and Reducing Questions
« Reply #1 on: November 29, 2009, 02:59:58 AM »
Redox reactions are fun; just remember LEO GER (loss electrons oxidation, gain electrons reduction) and that reducing agents are oxidized and oxidizing agents are reduced.  Whichever element gains electrons [charge becomes less positive or more negative] is oxidized, making it the reducing agent.

Looking at the charge on Mn in #1:
MnO4-  Mn2+
Since the overall charge on the reactant-side molecule is -1 and O is always -2,   Mn + (4 x -2) = -1     Mn would have to be +7
Mn7+  Mn2+
To balance the charge, Mn7+ + 5e- Mn2+
Mn is gaining electrons; remember "GER."  And if reduction is occurring, MnO4- in this equation is the oxidizing agent.

Hopefully that helps!

#### entice

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##### Re: Oxidizing and Reducing Questions
« Reply #2 on: November 29, 2009, 05:30:34 AM »
Thanks pear, that helped a lot!

Can you correct me if I'm wrong for the following..
What is the oxidizing agent in the following chemical reactions
2. 5S + 6KNO3 + 2CaCO3 -> 3K2SO4 + 2CaSO4 + CO2 +3N2
KNO3 is the oxidizing agent

What is the reducing agent in the following chemical reaction
1. 5Fe2+(aq) + MnO4-(aq) + 8H+(aq) -> 5Fe3+(aq) + Mn2+(aq) + 4H2O(l)
H+ is the reducing agent

What element is oxidized in the following chemical reaction
1. NiO2 + Cd + 2H2O -> Ni(OH)2 + Cd(OH)2
Is not a redox reaction

#### Borek

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##### Re: Oxidizing and Reducing Questions
« Reply #3 on: November 29, 2009, 07:11:44 AM »
KNO3 is the oxidizing agent

Unfortunately, that's the only correct answer so far.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

#### entice

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##### Re: Oxidizing and Reducing Questions
« Reply #4 on: November 29, 2009, 06:44:57 PM »
What is the reducing agent in the following chemical reaction
1. 5Fe2+(aq) + MnO4-(aq) + 8H+(aq) -> 5Fe3+(aq) + Mn2+(aq) + 4H2O(l)
Fe2+
+2 -> +3

What element is oxidized in the following chemical reaction
1. NiO2 + Cd + 2H2O -> Ni(OH)2 + Cd(OH)2
Cd
0 -> +2

I should be right this time?

#### Borek

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##### Re: Oxidizing and Reducing Questions
« Reply #5 on: November 29, 2009, 06:53:04 PM »
Looks OK this time.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

#### pear

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##### Re: Oxidizing and Reducing Questions
« Reply #6 on: November 29, 2009, 10:28:43 PM »
Yay!  Go through the steps and it's easy as pie.  I had a terrible time learning how to recognize them until someone told me to do the individual steps.  DO IT!