An organic pesticide (MW 183.7) is 8.43% Cl. A 0.627-g sample containing the pesticide plus inert material containing no chloride was decomposed with metallic sodium in alcohol. The liberated chloride ion was precipitated as AgCl weighing 0.0831 g. Calculate the percentage of pesticide in the sample.
mass AgCl = 0.0831 g.
moles AgCl = 0.0831/molar mass AgCl = ?
moles AgCl = moles Cl.
?moles Cl x atomic mass Cl = g Cl.
%Cl = (g Cl/g pesticide)*100 = 8.43%
You have %Cl and g Cl, solve for g pesticide, then
%pesticide = (g pesticide/g sample)*100 = ?
Check my work.
Thanks :d
To calculate the percentage of pesticide in the sample, we need to determine the amount of chlorine (Cl) in the pesticide and the sample.
1. Calculate the moles of AgCl formed:
- The molar mass of AgCl = 107.87 + 35.45 = 143.32 g/mol.
- Moles of AgCl = mass / molar mass = 0.0831 g / 143.32 g/mol = 0.00058 mol.
2. Calculate the moles of Cl in the AgCl:
- Since AgCl has a 1:1 mole ratio with Cl, the moles of Cl = 0.00058 mol.
3. Calculate the moles of Cl in the pesticide:
- Moles of Cl in the pesticide = moles of Cl in AgCl = 0.00058 mol.
4. Calculate the moles of the pesticide:
- The molar mass of the pesticide = 183.7 g/mol.
- Moles of the pesticide = (moles of Cl in the pesticide) / (moles of Cl per mole of pesticide)
= (0.00058 mol) / (0.0843 mol Cl/mol) = 0.00688 mol.
5. Calculate the mass of the pesticide:
- Mass of the pesticide = moles of the pesticide × molar mass
= 0.00688 mol × 183.7 g/mol = 1.263 g.
6. Calculate the percentage of pesticide in the sample:
- Percentage of pesticide = (mass of the pesticide / mass of the sample) × 100%
= (1.263 g / 0.627 g) × 100% = 201.27%.
Therefore, the percentage of pesticide in the sample is approximately 201.27%.
To calculate the percentage of the pesticide in the sample, we need to determine the amount of chloride that comes from the pesticide and then use that information to calculate the amount of pesticide in the sample.
Let's break down the problem step by step:
Step 1: Calculate the amount of Cl in the precipitated AgCl.
We know that the mass of AgCl is 0.0831 g. Since AgCl has a 1:1 ratio with Cl, the amount of Cl in AgCl is also 0.0831 g.
Step 2: Convert the amount of Cl to the amount of pesticide.
The Cl in AgCl comes from the pesticide. The molar mass of Cl is 35.45 g/mol. Since AgCl has a 1:1 ratio with Cl, the molar mass of AgCl is also 35.45 g/mol.
First, calculate the number of moles of Cl in AgCl:
moles of Cl = mass of Cl / molar mass of Cl
moles of Cl = 0.0831 g / 35.45 g/mol
Step 3: Calculate the amount of pesticide in the sample.
Now, we'll use the fact that there is 8.43% Cl by mass in the pesticide to calculate the mass of pesticide in the sample.
Let x be the mass of the pesticide in the 0.627 g sample. Since the pesticide is 8.43% Cl by mass, the mass of Cl from the pesticide is 0.0843 * x.
From Step 2, we know that the moles of Cl from AgCl is equal to the moles of Cl from the pesticide. Since moles = mass / molar mass, we can set up an equation:
moles of Cl from AgCl = moles of Cl from the pesticide
0.0831 g / 35.45 g/mol = (0.0843 * x) / 35.45 g/mol
Solving for x:
0.0831 g * 35.45 g/mol = 0.0843 * x
2.943 g/mol = 0.0843 * x
Now, solve for x:
x = (2.943 g/mol) / 0.0843
Step 4: Calculate the percentage of pesticide in the sample.
Now that we know the mass of the pesticide, x, we can calculate the percentage of pesticide in the sample.
percentage of pesticide = (mass of pesticide / mass of sample) * 100
percentage of pesticide = (x / 0.627 g) * 100
Substitute the value of x that we calculated:
percentage of pesticide = ((2.943 g/mol) / 0.0843) / 0.627 g * 100
Finally, calculate the percentage:
percentage of pesticide ≈ 54.89%
Therefore, the percentage of pesticide in the sample is approximately 54.89%.