A solution of iron(III) nitrate, Fe(NO3)3, was mixed with a solution of potassium carbonate, K2CO3. A precipitate was formed. What is the chemical formula of the precipitate?

Chemical formula of the precipitate is Fe(OH)₃

Explanation:

Fe(NO₃)₃ and K₂CO₃ are strong electrolytes and completely dissociates in water. Carbonate ions is a weak base and combines with water to form hydroxide ions (OH⁻), as follows

CO₃²⁻ +  H₂O <>  HCO₃⁻ + OH⁻

Ferric, Fe (III), combines with these hydroxide ions to form insoluble precipitates. Fe(OH)₃ is only partially soluble i.e., it does not completely dissociate in water. When the solutions of Fe(NO₃)₃ and K₂CO₃ are mixed together, Fe(OH)₃ precipitates out due to the strong electrostatic attraction between Fe (III) and hydroxide ions.  

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.