Precipitation process
When one solution is added to another, reaction may occur to cause the mixture to go cloudy or to produce a solid that settles on the bottom of the container. In either case precipitation is said to have occurred, and the insoluble substance produced in the reaction is referred to as a precipitate.
When the two solutions each contain ionic solids, the precipitate is also an ionic solid that exists as a lattice, that is an infinite regular arrangement of ions in which the cations of one of the ionic solids mixed is surrounded by the anions of the other and vice versa. You will see formation of a lattice of AgCl in the video.
The video below shows an animation of the precipitation of AgCl that occurs on mixing aqueous AgNO3 and NaCl.
The equation for the reaction that occurs is:
Ag+(aq) + Cl–(aq)
AgCl(s)
The (aq) means aqueous and represents the water molecules surrounding each ion in the solution.
When the two solutions each contain ionic solids, the precipitate is also an ionic solid that exists as a lattice, that is an infinite regular arrangement of ions in which the cations of one of the ionic solids mixed is surrounded by the anions of the other and vice versa. You will see formation of a lattice of AgCl in the video.
The video below shows an animation of the precipitation of AgCl that occurs on mixing aqueous AgNO3 and NaCl.
The equation for the reaction that occurs is:
Ag+(aq) + Cl–(aq)
AgCl(s)The (aq) means aqueous and represents the water molecules surrounding each ion in the solution.
VisChem molecular animations courtesy of Dr Roy Tasker,
University of Western Sydney.
1995.
University of Western Sydney.
1995.Use the controls beneath the image to play the video.
The spheres represent
| Silver Ag+ | Green Cl– | |
| Red O | White H | Bright blue N |
Note that:
The pair of ions that form the insoluble solid are attracted to each other to a greater extent than they are attracted to water. Thus collision between these ions results in a lattice.
The other pair of ions (Na+ and the bright blue and red NO3– ions in this case) remain unchanged.
The pair of ions that form the insoluble solid are attracted to each other to a greater extent than they are attracted to water. Thus collision between these ions results in a lattice.
The other pair of ions (Na+ and the bright blue and red NO3– ions in this case) remain unchanged.