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--EXPLAIN IT WITH MOLECULES -- INTERACTIVE MOLECULES -- WATER


Why is water such a good solvent?

 

[Water Molecule is shown using the JMol Applet]

To rotate click left mouse button over image and drag cursor. Zoom with middle button...


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Render -->Scheme -->CPK

Use left mouse button to rotate


 

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A water molecule is formed when two atoms of hydrogen bond covalently with an atom of oxygen. In a covalent bond electrons are shared between atoms. In water the sharing is not equal. The oxygen atom attracts the electrons more strongly than the hydrogen. This gives water an asymmetrical distribution of charge. Molecules that have ends with partial negative and positive charges are known as polar molecules. It is this polar property that allows water to separate polar solute molecules and explains why water can dissolve so many substances.

Water is a good solvent due to its polarity. The solvent properties of water are vital in biology, because many biochemical reactions take place only within aqueous solutions

When an ionic or polar compound enters water, it is surrounded by water molecules. The relatively small size of water molecules typically allows many water molecules to surround one molecule of solute. The partially negative dipoles of the water are attracted to positively charged components of the solute, and vice versa for the positive dipoles.

An example of an ionic solute is table salt.

Liquid water has a partially ordered structure in which hydrogen bonds are constantly being formed and breaking up.

The strong hydrogen bonds also give water a high cohesiveness and, consequently, surface tension. This is evident when small quantities of water are put onto a nonsoluble surface and the water stays together as drops.

 

What is the distance in angstroms for the hydrogen bond shown above?

 

[Water Molecule is shown using the JMol Applet]

To measure distance

Label the atoms:

Right mouse button -->Labels --> With atom names

Double click on hydrogen (H33) then drag to oxygen (O28) -- double click again


To measure angles

Double click on first atom, once on middle atom, twice on atom three.

 

1) What is the distance of the hydrogen bond show?

Please enter your answer in the space provided:


angstroms.

2) What is the measure of the HOH angle in a single molecule of water?

degrees.

3)What is distance between the oxygen atoms in a water dimer?

angstroms

Multiple Choice Questions

1. Water is considered a polar molecule because
a) the molecule has a net positive charge
b) the molecule has a net negative charge
c) the molecule has a net zero charge
d) the ends of the molecule have partial negative and positive charges

2. Hydrogen bonds in water are formed
a) only at very high temperatures
b) between two oxygen atoms
c) between a hydrogen atom of one water molecule and a hydrogen atom of another water molecule
d) between the hydrogen atom of one water molecule and the oxygen atom of another water molecule

3. The H-O-H angle formed is a(an):
a) acute angle
b) right angle
c) obtuse angle
d) reflex angle

4. The reason water droplets form is
a) gravity produces a drop when falling
b) strong hydrogen bonds give water a high cohesiveness
c) water is a non-polar compound
d) none of the above

5. Which of the following statements is correct
a) water is a solvent and table salt is a solute
b) table salt is a solvent and water is a solute
c) water and salt are both solvents
d) water and salt are both considered solutes


 


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