Question #e42f1

1 Answer
Mar 27, 2016

Here's what I got.

Explanation:

Silver nitrate, "AgNO"_3AgNO3, and potassium sulfide, "K"_2"S"K2S, are soluble ionic compounds, which means that they dissociate completely in aqueous solution to form cations and anions.

The two reactants can thus be represented as

"AgNO"_text(3(aq]) -> "Ag"_text((aq])^(+) + "NO"_text(3(aq])^(-)AgNO3(aq]Ag+(aq]+NO3(aq]

"K"_2"S"_text((aq]) -> 2"K"_text((aq])^(+) + "S"_text((aq])^(2-)K2S(aq]2K+(aq]+S2(aq]

When these two aqueous solutions are mixed, silver sulfide, "Ag"_2"S"Ag2S, an insoluble ionic compound that precipitates out of solution, will be formed.

In addition to silver sulfide, the reaction will also produce aqueous potassium nitrate, "KNO"_3KNO3, which will exist as dissociated cations and anions in solution.

The complete ionic equation looks like this

color(red)(2)"Ag"_text((aq])^(+) + color(red)(2)"NO"_text(3(aq])^(-) + 2"K"_text((aq])^(+) + "S"_text((aq])^(2-) -> "Ag"_color(red)(2)"S"_text((s]) darr + 2"K"_text((aq])^(+) + color(red)(2)"NO"_text(3(aq])^(-)2Ag+(aq]+2NO3(aq]+2K+(aq]+S2(aq]Ag2S(s]+2K+(aq]+2NO3(aq]

In order to get the net ionic equation, you must remove the spectator ions, i.e. the ions that are present on both sides of the equation.

You will have

color(red)(2)"Ag"_text((aq])^(+) + color(red)(cancel(color(black)(color(red)(2)"NO"_text(3(aq])^(-)))) + color(blue)(cancel(color(black)(2"K"_text((aq])^(+)))) + "S"_text((aq])^(2-) -> "Ag"_color(red)(2)"S"_text((s]) darr + color(blue)(cancel(color(black)(2"K"_text((aq])^(+)))) + color(red)(cancel(color(black)(color(red)(2)"NO"_text(3(aq])^(-))))

This will get you

color(green)(|bar(ul(color(white)(a/a)color(black)(color(red)(2)"Ag"_text((aq])^(+) + "S"_text((aq])^(2-) -> "Ag"_color(red)(2)"S"_text((s]) darr)color(white)(a/a)|)))

It's worth noting that silver sulfide is a black precipitate.

![archives.library.illinois.eduarchives.library.illinois.edu)

When aqueous solutions of calcium hydroxide, "Ca"("OH")_2, and sodium phosphate, "Na"_3"PO"_3, are mixed, the insoluble solid calcium phosphate, "Ca"_2("PO"_4)_3, and aqueous sodium hydroxide, "NaOH", are formed.

The complete ionic equation looks like this - keep in mind that you have color(red)(3 calcium cations and color(blue)(2) phosphate anions in calcium phosphate, "Ca"_color(red)(3)("PO"_4)_color(blue)(2)

color(red)(3)"Ca"_text((aq])^(2+) + (color(red)(3) xx 2)"OH"_text((aq])^(-) + (color(blue)(2) xx 3)"Na"_text((aq])^(+) + color(blue)(2)"PO"_text(4(aq])^(3-) -> "Ca"_3("PO"_4)_text(2(s]) darr + (color(blue)(2) xx 3)"Na"_text((aq])^(+) + (color(red)(3) xx 2)"OH"_text((aq])^(-)

The net ionic equation will be

color(red)(3)"Ca"_text((aq])^(2+) + color(purple)(cancel(color(black)((color(red)(3) xx 2)"OH"_text((aq])^(-)))) + color(brown)(cancel(color(black)((color(blue)(2) xx 3)"Na"_text((aq])^(+)))) + color(blue)(2)"PO"_text(4(aq])^(3-) -> "Ca"_3("PO"_4)_text(2(s]) darr + color(brown)(cancel(color(black)((color(blue)(2) xx 3)"Na"_text((aq])^(+)))) + color(purple)(cancel(color(black)((color(red)(3) xx 2)"OH"_text((aq])^(-))))

which is equivalent to

color(green)(|bar(ul(color(white)(a/a)color(black)(color(red)(3)"Ca"_text((aq])^(2+) + color(blue)(2)"PO"_text(4(aq])^(3-) -> "Ca"_3("PO"_4)_text(2(s]) darr)color(white)(a/a)|)))

Calcium phosphate is a white precipitate.