Phosgenite, a lead compound with the formula Pb2Cl2CO3, is found in Egyptian cosmetics. Phosgenite was prepared by the reaction of PbO, NaCl , and CO2. An unbalanced equation of the reactant mixture is PbO (s) + NaCl (aq) + H2O (l) + CO2 (g) \rightarrow Pb2Cl2CO3 (s) + NaOH (aq)
How many grams of phosgenite can be obtained from 10.0 g of PbO and 10.0 g of NaCl in the presence of excess water and CO2?
To determine the grams of phosgenite that can be obtained from 10.0 g of PbO and 10.0 g of NaCl, we need to follow these steps:
Step 1: Calculate the number of moles of PbO and NaCl
To find the moles of a substance, we can use the formula:
moles = mass / molar mass
The molar mass of PbO can be determined by summing the atomic masses of lead (Pb) and oxygen (O):
PbO molar mass = (atomic mass of Pb) + (atomic mass of O)
Similarly, the molar mass of NaCl can be calculated by adding the atomic masses of sodium (Na) and chlorine (Cl):
NaCl molar mass = (atomic mass of Na) + (atomic mass of Cl)
Step 2: Identify the limiting reactant
To determine the limiting reactant, we compare the moles of each reactant to the stoichiometric ratio given by the balanced equation. The reactant that produces fewer moles of the product is the limiting reactant.
In this case, the balanced equation provides a 1:1:1:1 stoichiometric ratio between PbO, NaCl, H2O, and CO2 with respect to the formation of phosgenite (Pb2Cl2CO3). Therefore, we will compare the moles of PbO and NaCl.
Step 3: Calculate the theoretical moles of phosgenite
Since PbO and NaCl have a 1:1 stoichiometric ratio with phosgenite, the theoretical moles of phosgenite formed will be equal to the moles of the limiting reactant.
Step 4: Convert moles of phosgenite to grams
To determine the mass of phosgenite formed, we can use the formula:
mass = moles × molar mass
The molar mass of phosgenite (Pb2Cl2CO3) can be calculated by summing the atomic masses of lead (Pb), chlorine (Cl), and carbon (C), and multiplying them by 2 due to the subscripts in the chemical formula.
Let's calculate the values:
Step 1:
Molar mass of PbO = (atomic mass of Pb) + (atomic mass of O)
= (207.2 g/mol) + (16.0 g/mol)
= 223.2 g/mol
Molar mass of NaCl = (atomic mass of Na) + (atomic mass of Cl)
= (23.0 g/mol) + (35.5 g/mol)
= 58.5 g/mol
moles of PbO = 10.0 g / 223.2 g/mol
≈ 0.0448 mol
moles of NaCl = 10.0 g / 58.5 g/mol
≈ 0.171 mol
Step 2:
Comparing the moles of PbO and NaCl, we see that PbO has the lower value, so it is the limiting reactant.
Step 3:
moles of phosgenite formed = moles of PbO
≈ 0.0448 mol
Step 4:
Molar mass of Pb2Cl2CO3 = (2 × atomic mass of Pb) + (2 × atomic mass of Cl) + (atomic mass of C) + (3 × atomic mass of O)
= (2 × 207.2 g/mol) + (2 × 35.5 g/mol) + (12.0 g/mol) + (3 × 16.0 g/mol)
= 465.9 g/mol
mass of phosgenite formed = moles of phosgenite × molar mass of Pb2Cl2CO3
≈ 0.0448 mol × 465.9 g/mol
≈ 20.89 g
Therefore, approximately 20.89 grams of phosgenite can be obtained from 10.0 grams of PbO and 10.0 grams of NaCl in the presence of excess water and CO2.
To determine the number of grams of phosgenite that can be obtained from 10.0 g of PbO and 10.0 g of NaCl, we will follow the steps outlined below:
Step 1: Convert the given masses of PbO and NaCl to moles.
Step 2: Determine the limiting reactant.
Step 3: Calculate the number of moles of phosgenite produced from the limiting reactant.
Step 4: Convert the moles of phosgenite obtained to grams.
Step 1: Convert the given masses of PbO and NaCl to moles.
The molar mass of PbO is: 207.2 g/mol (Pb) + 16.0 g/mol (O) = 223.2 g/mol
Number of moles of PbO = Mass of PbO / Molar mass of PbO
= 10.0 g / 223.2 g/mol
= 0.0448 mol
The molar mass of NaCl is: 22.99 g/mol (Na) + 35.45 g/mol (Cl) = 58.44 g/mol
Number of moles of NaCl = Mass of NaCl / Molar mass of NaCl
= 10.0 g / 58.44 g/mol
= 0.171 mol
Step 2: Determine the limiting reactant.
To find the limiting reactant, we need to compare the stoichiometric coefficients of PbO and NaCl in the balanced equation.
The balanced equation is:
PbO (s) + 2 NaCl (aq) + H2O (l) + CO2 (g) → Pb2Cl2CO3 (s) + NaOH (aq)
From the balanced equation, the stoichiometric coefficient ratio between PbO and NaCl is 1:2. This means that 1 mole of PbO reacts with 2 moles of NaCl.
Therefore, the mole ratio of PbO to NaCl is 0.0448 mol : 0.171 mol, which simplifies to approximately 1:4.
Since the mole ratio is greater than 1 for both reactants, we can conclude that NaCl is the limiting reactant because we have only 0.0448 mol of PbO available compared to 0.171 mol of NaCl.
Step 3: Calculate the number of moles of phosgenite produced from the limiting reactant.
From the balanced equation, the stoichiometric coefficient ratio between NaCl and Pb2Cl2CO3 is 2:1. This means that 2 moles of NaCl react to produce 1 mole of Pb2Cl2CO3.
Therefore, the number of moles of Pb2Cl2CO3 produced can be calculated as follows:
Number of moles of Pb2Cl2CO3 = (0.171 mol NaCl) / (2 mol NaCl/1 mol Pb2Cl2CO3)
= 0.0855 mol Pb2Cl2CO3
Step 4: Convert the moles of phosgenite obtained to grams.
To calculate the mass of Pb2Cl2CO3, we will use the formula:
Mass (g) = Number of moles × Molar mass
The molar mass of Pb2Cl2CO3 is: 2 × (207.2 g/mol Pb) + 2 × (35.45 g/mol Cl) + 3 × (16.0 g/mol O) + 12.01 g/mol C
= 846.62 g/mol
Mass of Pb2Cl2CO3 = 0.0855 mol × 846.62 g/mol
= 72.396 g
Therefore, approximately 72.4 grams of phosgenite can be obtained from 10.0 g of PbO and 10.0 g of NaCl in the presence of excess water and CO2.
2PbO(s) + 2NaCl(aq) + H2O(l) + CO2(g)==> Pb2Cl2CO3(s) + 2NaOH(aq)
This is a limiting reagent problem(LR).
mols PbO = grams/molar mass = ?
mols NaCl = grams/molar mass = ?
Using the coefficients in the balanced equation, convert mols PbO to mols of your product.
Do the same and convert mols NaCl to mols of your product.
It is likely that mols of the product will not be the same. In LR problems, the SMALLER number is always the correct one and the reagent producing that number is the LR.
Using the smaller number of moles of phosgenite, convert to grams.
grams = mols x molar mass = ?