Why do some combinations of ionic compounds form a precipitate while others do not

Whether or not such a reaction occurs can be determined by using the solubility rules for common ionic solids.

tell me if i'm wrong

This is because of the solubility of the reacting metal salts.

Explanation:

The use of solubility of salts influences the formation of precipitates. Most precipitation reactions occur as a result of the replacement reactions or double placement reactions. A double replacement reaction occurs when two ionic reactants dissociate and bond with respective anion and cation of the other reactant. This is simply a switch over reaction.

A double replacement reaction occurs when a chemical reaction occurs and one of the products formed is insoluble.

Here is an example:

Both reactants are acqeous and the product is solid.

first let us lay out the formula for potential

and kinetic energy:

pe = mgh

ke = (mv^2)/2

where: m=mass, v=velocity, g=gravitational

acceleration, h=height

calculating for mass using the known values of

pe:

340j = m (9.81 m/s^2) (50ft) (1m/3.28ft)

m = 2.27 kg

the law of conservation of energy states that

energy is neither created nor destroyed. therefore, the change in kinetic

energy from 50 ft to 35 ft would be equal to the change in potential energy

from 50 ft to 35 ft. however it would be opposite in signs since one is losing

while other is gaining.

ke(35ft) – ke(50ft) = - [ pe(35ft) – pe(50ft]

ke(50ft) = 0 since the brick is initially at rest

ke(35ft) = 340j - 2.27kg (9.81 m/s^2) (35ft)

(1m/3.28 ft)

ke(35ft)

= 102.38 j