The concentration of Pb2+ in a sample of wastewater is to be determined by using
gravimetric analysis. To a 100.0-mL sample of the wastewater is added an excess of
sodium carbonate, forming the insoluble lead (II) carbonate (267.2092 g/mol) according to
the balanced equation given below. The solid lead (II) carbonate is dried, and its mass is
measured to be 0.4078 g. What was the concentration of Pb2+ in the original wastewater
sample?
The M of Na2CO3 is .0054M. I don’t know what’s next. I think that that’s the answer.
To determine the concentration of Pb2+ in the original wastewater sample, we'll follow these steps:
Step 1: Calculate the moles of PbCO3 formed.
Step 2: Calculate the moles of Pb2+ in the original wastewater sample.
Step 3: Calculate the concentration of Pb2+ in the wastewater sample.
Step 1: Calculate the moles of PbCO3 formed.
The molar mass of PbCO3 is 267.2092 g/mol.
The mass of PbCO3 formed is 0.4078 g.
Moles of PbCO3 = mass / molar mass
Moles of PbCO3 = 0.4078 g / 267.2092 g/mol
Step 2: Calculate the moles of Pb2+ in the original wastewater sample.
According to the balanced equation, the stoichiometric ratio between PbCO3 and Pb2+ is 1:1.
Moles of Pb2+ = Moles of PbCO3
Step 3: Calculate the concentration of Pb2+ in the wastewater sample.
The volume of the sample used is 100.0 mL, which is equivalent to 0.1000 L.
Concentration of Pb2+ = Moles of Pb2+ / Volume of sample (in L)
Concentration of Pb2+ = Moles of Pb2+ / 0.1000 L
By following these steps, you can calculate the concentration of Pb2+ in the original wastewater sample.
To determine the concentration of Pb2+ in the original wastewater sample, we need to follow these steps:
1. Write the balanced chemical equation:
Pb2+ (aq) + CO32- (aq) -> PbCO3 (s)
2. Determine the moles of PbCO3 formed:
First, calculate the molar mass of PbCO3:
Molar mass of PbCO3 = 207.2 g/mol + 12.0 g/mol + 48.0 g/mol = 267.2092 g/mol
Next, use the given mass of PbCO3 (0.4078 g) to find the number of moles:
Moles of PbCO3 = mass of PbCO3 / molar mass of PbCO3
3. Convert moles of PbCO3 to moles of Pb2+:
From the balanced chemical equation, we see that the mole ratio between Pb2+ and PbCO3 is 1:1. Therefore, the moles of Pb2+ will be equal to the moles of PbCO3.
4. Calculate the volume of the original wastewater sample:
Since we are given the volume of the sample (100.0 mL), we don't need to convert to volume.
5. Calculate the concentration of Pb2+:
Concentration = Moles of Pb2+ / Volume of sample
Now let's go through the calculations:
Molar mass of PbCO3 = 267.2092 g/mol
Mass of PbCO3 = 0.4078 g
Moles of PbCO3 = 0.4078 g / 267.2092 g/mol
Moles of Pb2+ = Moles of PbCO3 = 0.4078 g / 267.2092 g/mol
Volume of sample = 100.0 mL
Concentration of Pb2+ = Moles of Pb2+ / Volume of sample
Plug in the values:
Concentration of Pb2+ = (0.4078 g / 267.2092 g/mol) / 100.0 mL
Now you can solve the equation to find the concentration of Pb2+ in the original wastewater sample.