A5.000 g mixture contains strontium nitrate and potassium bromide. excess lead(ii) nitrate solution is added to precipitate out 0.7822 grams of lead(ii) bromide. what is the percent by mass of potassium bromide in the mixture?

The mass percent of potassium bromide in the mixture is 9.996%

Explanation:

    .....(1)

For lead (II) bromide:

Given mass of lead (II) bromide = 0.7822 g

Molar mass of lead (II) bromide = 367 g/mol

Putting values in equation 1, we get:

By Stoichiometry of the reaction:

1 mole of lead (II) bromide is produced from 2 moles of potassium bromide

So, 0.0021 moles of lead (II) bromide will be produced from = of potassium bromide

Molar mass of KBr = 119 g/mol

Moles of KBr = 0.0042 moles

Putting values in equation 1, we get:

Mass of mixture = 5.000 g

Mass of KBr = 0.4998 g

Putting values in above equation, we get:

Hence, the percent by mass of KBr in the mixture is 9.996 %