When does a precipitate form?

Answer 1

Form a new insoluble compoundWhen you mix two solutions of different ionic compounds that individually are soluble compounds, they form an new insoluble compound which produces a precipitate.

Let me illustrate with an example: Let's say you have solution of something we'll call AB and another of CD (just made up names), where both AB and CD are soluble. In one solution you'd have A+ and B- ions, and in the other you'd have C+ and D- ions. When you mix the two solutions, you'd have all four types of ions in the same solution. But let's say that compound AD is NOT soluble. Whenever an A+ ion encounters a D- ion in the solution, they will stick together and form this insoluble compound AD. Because it is insoluble, it will form a solid, and that solid is the precipitate you see.

If, using this same example, all of the possible combinations of ions, in other words AB, AD, CD, and CB are soluble compounds, then you will not form a precipitate when you mix them because when the ions meet, even if they come together momentarily, they will just as quickly redissolve.

by Jwoodw4 :)

Answer 2

A precipitate forms when a solute can not be dissolved in a solution. The solubility rules can help you to see if a solute is soluble or not soluble.

Chemical changes can form precipitates as compounds that are not soluble in the current solution. Mixing of solutions can cause precipitates where one compound is more soluble than another. Physical changes can cause a compound to come out of a solution (usually a reduction in solution temperature).

Answer 3

There is more than one reason why a precipitate can form. A chemical reaction that involves dissolved chemicals can produce a product that is not soluble, or is not as soluble as the reactants were. Or, even if you have a soluble chemical, if the concentration is too high, or if the temperature drops, you can still get a precipitation.

Answer 4

As far as I understand, this word is used mostly in science. When some substance is not soluable in the water or other liquid phase, it will aggregate and sink given its density is higher than liquid phase.

Answer 5

A precipitate is a solid compound that comes out of a solution, due to either physical changes in the solution or to chemical changes that form a new compound.

Answer 6

by seprating

Answer 7

its because they are insoluble