The concentration of Pb+2 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 insoluable 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 0.6885 g. What was the concentration of Pb+2 in the original wastewater sample ?

Question

The concentration of Pb+2 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 insoluable 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 0.6885 g. What was the concentration of Pb+2 in the original wastewater sample ?

Pb+2(aq)+Na2CO3(aq)->PbCO3(s)+2Na+(aq)

Answer 1

mass Pb = mass PbCO3 x (atomic mass Pb/molar mass PbCO3) = ?

(Pb^2+) = mass Pb^2+/0.1L = ? in moles/L

Answer 2

To determine the concentration of Pb+2 in the original wastewater sample, we can use the information about the mass of the dried lead(II) carbonate precipitate.

Here's how you can solve the problem step by step:

Step 1: Calculate the moles of lead(II) carbonate (PbCO3).
The molar mass of PbCO3 is given as 267.2092 g/mol.
Using the mass of the dried precipitate (0.6885 g), we can calculate the number of moles:
moles of PbCO3 = mass / molar mass = 0.6885 g / 267.2092 g/mol

Step 2: Determine the moles of Pb2+ in the original wastewater sample.
From the balanced equation, we can see that 1 mole of PbCO3 corresponds to 1 mole of Pb2+.
Therefore, the number of moles of Pb2+ in the original sample is equal to the moles of PbCO3.

Step 3: Calculate the volume of the original wastewater sample.
The given volume of the sample is 100.0 mL, which is equivalent to 0.1000 L.

Step 4: Calculate the concentration (molarity) of Pb2+.
The concentration (molarity) is defined as moles of solute divided by the volume of the solution in liters.
Concentration (molarity) of Pb2+ = moles of Pb2+ / volume of solution in liters = moles of PbCO3 / 0.1000 L

Step 5: Plug in the values and calculate the concentration.
Substitute the calculated values into the equation from step 4 and solve for the concentration:
Concentration (molarity) of Pb2+ = (0.6885 g / 267.2092 g/mol) / 0.1000 L

Calculate this expression to find the concentration of Pb2+ in the original wastewater sample.

Remember to express your final answer with the correct number of significant figures based on the given data and the appropriate unit (mol/L or M).