Ch109_LectureNotes

MnO₄^- + Cl^-

Mn²⁺ + Cl₂

First break the equation into two half reactions, one for Mn and one for Cl

MnO₄^- Mn²⁺

MnO₄^- Mn²⁺
MnO₄^- Mn²⁺ + 4 H₂O
8 H⁺ + MnO₄^- Mn²⁺ + 4 H₂O
5 e^- + 8 H⁺ + MnO₄^- Mn²⁺ + 4 H₂O
10 e^- + 16 H⁺ + 2 MnO₄^- 2 Mn²⁺ + 8 H₂O

Cl^- Cl₂

2 Cl^- Cl₂
...
...
2 Cl^- Cl₂ + 2 e^-
10 Cl^- 5 Cl₂ + 10 e^-

10 e^- + 16 H⁺ + 2 MnO₈^-+ 10 Cl^- 2 Mn²⁺ + 8 H₂O + 5 Cl₂ + 10 e^-

16 H⁺ + 2 MnO₄^- + 10 Cl^- 2 Mn²⁺ + 8 H₂O + 5 Cl₂

Basic Solution:

Separate the reaction into two half-reactions.

Balance each half-reaction separately as in acid:

Balance atoms other than O & H by inspection.
Balance O by adding H₂O to the opposite side.
Balance H by addding H⁺ as appropriate.
Balance the charge by adding electrons (e^-) - add to same side as excess of positive charge, or opposite side if excess negative charge.
Balance the charges of the two half-reactions by multiplying appropriately.

Balance as in acid above, then:

Add enough OH^- (equal numbers to both sides) to cancel the H⁺. (This is necessary because there will not be protons present in a basic solution!). (There are a couple of other conventions for balancing in basic solutions. If you are familiar with another and prefer it, you may use it instead.)
Combine the H⁺ and OH^- on the appropriate side of the equation to give waters.
Go back and cancel waters which appear on both sides to give the final equation.

Water Properties

Extremely high mp and bp:

	MW	m.p.	b.p.
Water	18	0°C	100°C
Methane	16	-183°C	-161°C

High Heat capacity: 18 cal/°C mol vs. 8 cal/°C mol for methane
High viscosity
Solid form is less dense than the liquid form at the same temperature (ice floats on water - very rare)
High dielectric constant (78.5 vs. 1.9 for hexane; 'blocks electric fields')
High surface tension.

Structural diagram of water molecule showing bond angles and lengths

public domain image via Wikipedia Creative Commons

Space-filling image of water molecule

public domain image via Wikipedia Creative Commons

#-D image of H-bonding between space-filling images of water molecules

public domain image via Wikipedia Creative Commons

Flattened image of the hydration of sodium ion

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© R A Paselk

Last modified 16 February 2015

10 e- + 16 H+ + 2 MnO4- 2 Mn2+ + 8 H2O

10 Cl- 5 Cl2 + 10 e-

10 e- + 16 H+ + 2 MnO8-+ 10 Cl- 2 Mn2+ + 8 H2O + 5 Cl2 + 10 e-

16 H+ + 2 MnO4- + 10 Cl- 2 Mn2+ + 8 H2O + 5 Cl2

Basic Solution:

Separate the reaction into two half-reactions.

Balance each half-reaction separately as in acid:

Balance atoms other than O & H by inspection.

Balance O by adding H2O to the opposite side.

Balance H by addding H+ as appropriate.

Balance the charge by adding electrons (e-) - add to same side as excess of positive charge, or opposite side if excess negative charge.

Balance the charges of the two half-reactions by multiplying appropriately.

Balance as in acid above, then:

Add enough OH- (equal numbers to both sides) to cancel the H+. (This is necessary because there will not be protons present in a basic solution!). (There are a couple of other conventions for balancing in basic solutions. If you are familiar with another and prefer it, you may use it instead.)

Combine the H+ and OH- on the appropriate side of the equation to give waters.

Go back and cancel waters which appear on both sides to give the final equation.

Water Properties

Extremely high mp and bp:

MW

m.p.

b.p.

Water

18

0°C

100°C

Methane

16

-183°C

-161°C

High Heat capacity: 18 cal/°C mol vs. 8 cal/°C mol for methane

High viscosity

Solid form is less dense than the liquid form at the same temperature (ice floats on water - very rare)

High dielectric constant (78.5 vs. 1.9 for hexane; 'blocks electric fields')

High surface tension.

10 e^- + 16 H⁺ + 2 MnO₄^- 2 Mn²⁺ + 8 H₂O

10 Cl^- 5 Cl₂ + 10 e^-

10 e^- + 16 H⁺ + 2 MnO₈^-+ 10 Cl^- 2 Mn²⁺ + 8 H₂O + 5 Cl₂ + 10 e^-

16 H⁺ + 2 MnO₄^- + 10 Cl^- 2 Mn²⁺ + 8 H₂O + 5 Cl₂

Balance O by adding H₂O to the opposite side.

Balance H by addding H⁺ as appropriate.

Balance the charge by adding electrons (e^-) - add to same side as excess of positive charge, or opposite side if excess negative charge.

Add enough OH^- (equal numbers to both sides) to cancel the H⁺. (This is necessary because there will not be protons present in a basic solution!). (There are a couple of other conventions for balancing in basic solutions. If you are familiar with another and prefer it, you may use it instead.)

Combine the H⁺ and OH^- on the appropriate side of the equation to give waters.