A solution is a mixture of a solute (often a solid) dissolved in a solvent (usually a liquid).
Soluble substances dissolve to form clear (see-through) solutions. Solutions can be any colour.
Water is a common solvent.
In water molecules, the OH bonds are polar covalent.
Both hydrogens are on the same side of the oxygen in the water molecule. Water is referred to as a polar molecule because, as the electron density map shows, the H side of the water molecule is more positive, and the O side is more negative.
In solutions the solvent and the solute particles are attracted to one another.
Interaction of ions with water
Ionic solids exist as cations (positive) and anions (negative).
Ions exist in solution as hydrates. These are complexes with water and are written as M+(aq).or X–(aq).
Hydrated ions are complexes where the ion is surrounded by water (see diagram).
As shown, the orientation of the water molecules in the complex depends on the sign of the charge on the ion.
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Soluble substances dissolve to form clear (see-through) solutions. Solutions can be any colour.
In water molecules, the OH bonds are polar covalent.
Place your pointer over the diagram to see an electron density map showing regions of partial negative charge (δ–) at O and partial postive charge (δ+) at H.
Both hydrogens are on the same side of the oxygen in the water molecule. Water is referred to as a polar molecule because, as the electron density map shows, the H side of the water molecule is more positive, and the O side is more negative.
In solutions the solvent and the solute particles are attracted to one another.
Interaction of ions with waterIonic solids exist as cations (positive) and anions (negative).
Ions exist in solution as hydrates. These are complexes with water and are written as M+(aq).or X–(aq).
Hydrated ions are complexes where the ion is surrounded by water (see diagram).
Note that in an actual solution there are more than four water molecules around each one as there are water molecules both behind and in front of the ions shown in the diagram.
As shown, the orientation of the water molecules in the complex depends on the sign of the charge on the ion.
For cations (positive ions) the oxygen (more electron-rich atom of the water molecule) is closest to the ion.
For anions (negative ions) the hydrogen (more electron-poor atom of the water molecule) is closest to the ion.
For anions (negative ions) the hydrogen (more electron-poor atom of the water molecule) is closest to the ion.
Warning! The next two pages in this module may be slower to load because they include video files.