AgNO3 + NaBr = AgBr + NaNO3 | Silver Nitrate + Sodium Bromide Reaction

When aqueous silver nitrate (AgNO3) solution and aqueous sodium chloride (NaCl) compounds are mixed together, there is a high chance of giving a pale-yellow colour precipitate, silver bromide (AgBr) if silver cations and chloride ion concentrations are enough. This reaction can be used for as a testing of bromide ion.

AgNO3(aq) + NaBr(aq) = AgBr(s) + NaNO3(aq)

Both silver nitrate and sodium chloride solutions are colourless solutions. When they react with each other, pale-yellow colour precipitate and colourless solution is given. Due to formation of AgBr, pale-yellow precipitate is given and colourless solution contains NaNO3 and small amount of silver and bromide ions.

NaBr + AgNO3 - sodium bromide and silver nitrate reaction

Observations during the reaction

When you are slowly adding one chemical to other chemical drop by drop, at one time, you will see a pale-yellow precipitate is formed in the solution. If you add large amount of chemical to another, precipitate will be formed immediately. But, remember that to be careful with silver nitrate solution during the experiment because silver nitrate is highly corrosive and can cause gray pigmentation of the skin.

ZAgNO3 + NaCl reaction

What will happen if solid sodium bromide is added to aqueous AgNO3 solution?

Solid sodium bromide will immediately dissociates to sodium ions and bromide ions when it is added to silver nitrate solution. Then, due to presence of silver and bromide ions, silver bromide will be precipitated as usual.

Example of calculation to determine the required concentration to observe the precipitation of silver bromide

When similar volumes of NaBr and AgNO3 are mixed, will there be a precipitate? Both solutions have concentrations of 0.1 mol dm-3.

Let's think, when both solutions are mixed, there is no precipitate. Then, calculate concentration of each ion in the solution. Because each compound is diluted by two times, concentration of each ion should be reduced by half.

Concentration of each ion = 0.05 mol dm-3.

Then we can apply Ksp expression to check whether will there be a AgBr precipitate.

Initial Br- concentration after mixing = 0.05 mol dm-3

Initial Ag+ concentration after mixing = 0.05 mol dm-3

Ksp expression for AgBr = [Ag+(aq)][Br-(aq)]

[Ag+(aq)][Cl-(aq)] = 0.05 mol dm-3 * 0.05 mol dm-3

[Ag+(aq)][Cl-(aq)] = 2.5 * 10-3 mol2 dm-6

Ksp, AgBr = 7.7 * 10-13 mol2 dm-6

Because calculated value for Ksp expression is greater than Ksp value of AgBr. Therefore you can see AgBr is precipitated in the solution.

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