Question

Write the equation for the reaction, if any, that occurs when each of the following experiments is performed under standard conditions. (a) Crystals of iodine are added to an aqueous solution of potassium bromide. (b) Liquid bromine is added to an aqueous solution of sodium chloride. (c) A chromium wire is dipped into a solution of nickel(II) chloride.

Short answer

Answer: (a) No reaction occurs. (b) NaCl (aq) + Br2 (l) -> NaBr (aq) + Cl2 (g) (c) NiCl2 (aq) + Cr (s) -> Ni (s) + CrCl2 (aq)

Step-by-step solution

1. Identify the possible reactions and products for each experiment

For each experiment, we should identify the possible reactions and products, taking into consideration the solubility rules and the activity series. (a) When crystals of iodine are added to an aqueous solution of potassium bromide, the potassium bromide may dissolve and react with the iodine. Since both iodine and bromine are halogens, a halogen displacement reaction could occur if iodine is more reactive than bromine. KBr (aq) + I2 (s) -> KI (aq) + Br2 (l) (b) When liquid bromine is added to an aqueous solution of sodium chloride, a halogen displacement reaction could occur if bromine is more reactive than chlorine. NaCl (aq) + Br2 (l) -> NaBr (aq) + Cl2 (g) (c) When a chromium wire is dipped into a solution of nickel(II) chloride, a redox reaction could take place if chromium is more reactive than nickel. NiCl2 (aq) + Cr (s) -> Ni (s) + CrCl2 (aq)

2. Determine if the reactions will take place

We will use the activity series to determine if the reactions we identified in the first step will actually occur. The activity series is a list of elements that are organized from most reactive to least reactive. Halogens activity series: F2 > Cl2 > Br2 > I2 Metals activity series: ... Cr > ... > Ni > ... (a) In this case, iodine (I2) is less reactive than bromine (Br2), so the halogen displacement reaction will not occur. (b) In this case, bromine (Br2) is more reactive than chlorine (Cl2), so the halogen displacement reaction will occur. (c) In this case, chromium (Cr) is more reactive than nickel (Ni), so the redox reaction will occur.

3. Write the balanced chemical equations for the reactions that occur

Now that we know which reactions will occur, we can write the balanced chemical equations: (a) No reaction occurs. (b) NaCl (aq) + Br2 (l) -> NaBr (aq) + Cl2 (g) (c) NiCl2 (aq) + Cr (s) -> Ni (s) + CrCl2 (aq)