What precipitate will form when aqueous solutions of sodium carbonate calcium #Na_2CO_3# and calcium chloride #CaCl_2# are mixed?

Sodium carbonate, #"Na"_2"CO"_3#, and calcium chloride, #"CaCl"_2#, are soluble ionic compounds that dissociate in aqueous solution to form cations and anions.

You can thus say that the sodium carbonate solution will contain sodium cations, #"Na"^(+)#, and carbonate anions, #"CO"_3^(2-)#

#"Na"_ 2"CO"_ (3(aq)) -> 2"Na"_ ((aq))^(+) + "CO"_(3(aq))^(2-)#

Likewise, the calcium chloride solution will contain calcium cations, #"Ca"^(2+)#, and chloride anions, #"Cl"^(-)#

#"CaCl"_ (2(aq)) -> "Ca"_ ((aq))^(2+) + 2"Cl"_((aq))^(-)#

Now, when you mix these two solutions, the calcium cations will pair up with the carbonate anions and for calcium carbonate, #"CaCO"_3#, an insoluble ionic compound that precipitates out of solution.

This double replacement reaction will also produce aqueous sodium chloride.

The complete ionic equation looks like this

#2"Na"_ ((aq))^(+) + "CO"_ (3(aq))^(2-) + "Ca"_ ((aq))^(2+) + 2"Cl"_ ((aq))^(-) -> "CaCO"_ (3(s)) darr + 2"Na"_ ((aq))^(+) + 2"Cl"_ ((aq))^(-)#

Eliminate the spectator ions

#color(red)(cancel(color(black)(2"Na"_ ((aq))^(+)))) + "CO"_ (3(aq))^(2-) + "Ca"_ ((aq))^(2+) + color(red)(cancel(color(black)(2"Cl"_ ((aq))^(-)))) -> "CaCO"_ (3(s)) darr + color(red)(cancel(color(black)(2"Na"_ ((aq))^(+)))) + color(red)(cancel(color(black)(2"Cl"_ ((aq))^(-))))#