A 0.8870-g mixture of sodium chloride and potassium chloride is dissolved in water and silver nitrate is added. The AgCl that precipitates has a mass of 1.913 g. Calculate the percent by mass of potassium in the initial mixture。
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To calculate the percent by mass of potassium in the initial mixture, we need to determine the mass of potassium chloride present in the mixture.
Step 1: Calculate the mass of AgCl formed
Given that the mass of AgCl formed is 1.913 g.
Step 2: Calculate the moles of AgCl formed
The molar mass of AgCl is 143.32 g/mol.
Moles of AgCl = Mass of AgCl / Molar mass of AgCl
Moles of AgCl = 1.913 g / 143.32 g/mol
Step 3: Determine the moles of Cl- ions present
Since each mole of AgCl contains one Cl- ion,
Moles of Cl- ions = Moles of AgCl
Step 4: Determine the moles of KCl present
The molar mass of KCl is 74.55 g/mol.
Moles of KCl = Moles of Cl- ions
Step 5: Calculate the mass of KCl present
Mass of KCl = Moles of KCl x Molar mass of KCl
Mass of KCl = Moles of KCl x 74.55 g/mol
Step 6: Calculate the percent by mass of potassium in the mixture
Percent by mass of K = (Mass of KCl / Initial mass of mixture) x 100
Initial mass of mixture = Mass of KCl + Mass of NaCl
Percent by mass of K = (Mass of KCl / (Mass of KCl + Mass of NaCl)) x 100
Given that the initial mass of mixture is 0.8870 g.
Substituting the values into the equation:
Percent by mass of K = (Mass of KCl / (Mass of KCl + Mass of NaCl)) x 100
Percent by mass of K = (Mass of KCl / (0.8870 g)) x 100
Finally, substitute the calculated mass of KCl:
Percent by mass of K = (Moles of KCl x 74.55 g/mol / 0.8870 g) x 100
To determine the percent by mass of potassium in the initial mixture, we need to calculate the mass of potassium chloride (KCl) present.
1. Begin by finding the mass of the precipitated silver chloride (AgCl). Given that its mass is 1.913 g, this value represents the mass of chloride ions (Cl^-) in the mixture.
2. The molar mass of silver chloride (AgCl) is calculated by summing the atomic masses of the elements involved. Ag (silver) has a molar mass of 107.87 g/mol, while Cl (chlorine) has a molar mass of 35.45 g/mol. Therefore, the molar mass of AgCl is 143.32 g/mol.
3. Convert the mass of AgCl to moles. To do this, divide the mass of AgCl by its molar mass:
Moles of AgCl = mass of AgCl / molar mass of AgCl
In our case:
Moles of AgCl = 1.913 g / 143.32 g/mol
4. Since KCl contains only one chloride ion per formula unit, the moles of AgCl will also represent the moles of chloride ions in the mixture.
5. The molar mass of potassium chloride (KCl) is calculated by adding the atomic masses of potassium (K) and chlorine (Cl):
K (potassium) has a molar mass of 39.10 g/mol, while Cl (chlorine) has a molar mass of 35.45 g/mol. Therefore, the molar mass of KCl is 74.55 g/mol.
6. Calculate the mass of KCl in the initial mixture using the moles of chloride:
Mass of KCl = moles of chloride ions * molar mass of KCl
In our case:
Mass of KCl = (1.913 g / 143.32 g/mol) * 74.55 g/mol
7. Finally, calculate the percent by mass of potassium in the initial mixture by dividing the mass of KCl by the total mass of the mixture and multiplying by 100%
Percent by mass of potassium = (mass of KCl / total mass of mixture) * 100%
In our case:
Percent by mass of potassium = [(1.913 g / 143.32 g/mol) * 74.55 g/mol] / 0.8870 g * 100%
It is straightforward.
a) calculate themass of the chloride in the silver chloride.
b) calculate the chloride in .887g naCl
subtrace b from a
the remainder is cl in KCl. knowing that mass of chlorde ion, compute the mass of KCl.
a bit of math, but not rocket science here.