A 0.3146-g sample of a mixture of NaCl(s) and KBr(s) was dissolved in water. The resulting solution required 37.20 mL of 0.08765 M AgNO3(aq) to precipitate the Cl–(aq) and Br–(aq) as AgCl(s) and AgBr(s). Calculate the mass percentage of NaCl(s) in the mixture.
To find the mass percentage of NaCl in the mixture, we need to determine the amount of NaCl and KBr present in the sample.
First, let's calculate the number of moles of AgNO3 used in the titration. We have the concentration of AgNO3 and the volume used:
moles of AgNO3 = concentration * volume
= 0.08765 M * 0.03720 L
= 0.00325998 mol
Since AgNO3 reacts with both Cl- and Br-, we need to calculate the number of moles of Cl- and Br- present in the sample. Each mole of AgNO3 reacts with 1 mole of Cl- and 1 mole of Br-.
moles of Cl- and Br- = 0.00325998 mol
Next, let's calculate the molar mass of AgCl and AgBr. AgCl has a molar mass of 143.32 g/mol, and AgBr has a molar mass of 187.77 g/mol.
mass of AgCl = moles of Cl- * molar mass of AgCl
= 0.00325998 mol * 143.32 g/mol
= 0.467737 g
mass of AgBr = moles of Br- * molar mass of AgBr
= 0.00325998 mol * 187.77 g/mol
= 0.611079 g
Since AgCl and AgBr are the products of the reaction between AgNO3 and the chloride and bromide ions, the total mass of the precipitate is the sum of the masses of AgCl and AgBr.
mass of AgCl + AgBr = 0.467737 g + 0.611079 g
= 1.078816 g
Finally, the mass percentage of NaCl can be calculated using the following formula:
mass percentage of NaCl = (mass of NaCl / total mass of mixture) * 100%
We know that the total mass of the mixture is 0.3146 g, so we can substitute the values in the formula:
mass percentage of NaCl = (mass of NaCl / 0.3146 g) * 100%
Subtracting the mass of AgCl + AgBr from the total mass of the mixture gives us the mass of NaCl:
mass of NaCl = 0.3146 g - 1.078816 g
= -0.764216 g
However, the negative mass is not possible. This indicates that there was an error in the calculations, or the given data is incorrect. Please recheck the given data and calculations to find any mistakes.