A solution contains one or more of the following ions: silver, barium, and Copper (II). CY 105 student adds sodium chloride to a small sample of the solution of the unknown and a white precipitate is formed. He/she filters out the precipitate and then add sodium carbonate to the filtrate and observes a formation of blue precipitate. What ions were present in the unknown?

To find the ions, we need to know the properties of some metals.

Since we added chloride and carbonate ions and obtained precipitates, we need to know the solubilities and colours of the following salts: (S=soluble, I=insoluble)

Salt Solubility Colour
AgCl I White
CuCl2 S blue/green solution
BaCl2 S colourless solution

Salt Solubility Colour
Ag2CO3 I White
CuCO3 I blue (colour of oxidized copper roofs)
BaCO3 I white

Work with the tables above and solve the "puzzle" of the ions.

To determine which ions were present in the unknown solution, let's analyze the reactions that occurred.

1. Adding sodium chloride (NaCl) to the unknown solution resulted in the formation of a white precipitate. This indicates the presence of chloride ions (Cl-) reacting with one of the cations in the unknown solution to form an insoluble salt, a precipitate. The cation responsible for this reaction could be silver (Ag+).

2. After filtering out the white precipitate, sodium carbonate (Na2CO3) was added to the filtrate. A blue precipitate formed, indicating the presence of a cation that reacts with carbonate ions (CO3^2-) to form an insoluble salt. This cation is likely copper (Cu2+).

So, based on the observations, the unknown solution contains silver ions (Ag+) and copper ions (Cu2+).