Question

A mixture consisting of only potassium bromide (kbr) and sodium bromide (nabr) weighs 1.0584 g. when the mixture is dissolved in water and an excess of silver nitrate is added, all the bromide ions associated with the original mixture are precipitated as insoluble silver bromide (agbr). the mass of the silver bromide is found to be 1.8052 g. calculate the mass percentages of potassium bromide and sodium bromide in the original mixture.

Mass percent NaBr
Mass percent KBr

Answer 1

To calculate the mass percentages of KBr and NaBr in the original mixture, we need to determine the amount of each compound and the moles of AgBr formed. These moles will allow us to set up a system of equations that will help us find the values of x (the mass of KBr) and (1.0584 - x) (the mass of NaBr). Finally, we can calculate the mass percentages.

Step-by-step explanation:

To calculate the mass percentages of potassium bromide (KBr) and sodium bromide (NaBr) in the original mixture, we need to determine the amount of each compound present.

Let's assume the mass of KBr in the mixture is x g, and the mass of NaBr is (1.0584 - x) g.

When the mixture is dissolved in water and treated with silver nitrate, all the bromide ions from both KBr and NaBr precipitate as silver bromide (AgBr). The mass of the precipitated AgBr is 1.8052 g.

Since the molar mass of AgBr is 187.8 g/mol, we can calculate the number of moles of AgBr formed:

moles of AgBr = mass of AgBr / molar mass of AgBr = 1.8052 g / 187.8 g/mol = 0.0096 mol

Now, we can set up a system of equations:

For KBr: x g / molar mass of KBr = moles of AgBr = 0.0096 mol

For NaBr: (1.0584 - x) g / molar mass of NaBr = moles of AgBr = 0.0096 mol

By solving these equations simultaneously, we can find the values of x and (1.0584 - x).

Finally, we can calculate the mass percentages:

Mass percent NaBr = mass of NaBr / total mass of mixture * 100%

Mass percent KBr = mass of KBr / total mass of mixture * 100%