What is the limiting reactant if 0.500 g Aluminum is reacted with 3.500 g Copper (II) chloride (when calculating the molar mass of copper chloride you need to add mass of 2H2O because it is a dihydrate)?
2Al + 3CuCl2.2H2O ==> 3Cu + 2AlCl3 + 2H2O
mols Al = 0.500/27 = 0.0185
mols CuCl2.2H2O = 3.50/170 = 0.0205
mols Cu produced from 0.0185 mols Al could be 0.0185 x (3 mols Cu/2 mols Al) = 0.065
mols Cu produced from 0.0205 mols CuCl2.2H2O could be 0.0205 x (mol Cu/1 mol CuCl2.2H2O) = .0205
In limiting reagent problems you can't produce more than the smallest amount; therefore, CuCl2.2H2O is the LR.
Check all of these calculations.
To determine the limiting reactant, we need to compare the number of moles of each reactant and calculate the mole ratios based on the balanced chemical equation.
First, let's calculate the number of moles of Aluminum (Al):
1. Determine the molar mass of Aluminum (Al) from the periodic table.
- The molar mass of Al is approximately 26.98 g/mol.
2. Use the formula: moles = mass / molar mass.
- moles of Al = 0.500 g / 26.98 g/mol
Next, let's calculate the number of moles of Copper (II) chloride (CuCl2·2H2O):
1. Determine the molar mass of Copper (II) chloride (CuCl2·2H2O).
- The molar mass of CuCl2·2H2O is the sum of the molar mass of CuCl2 and two times the molar mass of water (H2O).
- The molar mass of CuCl2 is approximately 134.45 g/mol.
- The molar mass of H2O is approximately 18.02 g/mol.
- Therefore, the molar mass of CuCl2·2H2O is approximately 170.45 g/mol.
2. Use the formula: moles = mass / molar mass.
- moles of CuCl2·2H2O = 3.500 g / 170.45 g/mol.
Now that we have the number of moles of each reactant, we can calculate the mole ratios based on the balanced chemical equation.
The balanced chemical equation for the reaction is:
2Al + 3CuCl2 -> 2AlCl3 + 3Cu
The stoichiometric ratio between Aluminum (Al) and Copper (II) chloride (CuCl2) is 2:3. This means that for every 2 moles of Aluminum, we need 3 moles of Copper (II) chloride.
Let's compare the mole ratios:
Moles of Al: 0.500 g / 26.98 g/mol
Moles of CuCl2: 3.500 g / 170.45 g/mol
Now, divide the number of moles of each reactant by their respective stoichiometric coefficient in the balanced equation.
Moles of Al / Coefficient of Al: 0.500 g / 26.98 g/mol / 2
Moles of CuCl2 / Coefficient of CuCl2: 3.500 g / 170.45 g/mol / 3
Compare the resulting values of the two calculations:
Moles of Al / Coefficient of Al =
(0.500 g / 26.98 g/mol) / 2 = 0.00926 mol
Moles of CuCl2 / Coefficient of CuCl2 =
(3.500 g / 170.45 g/mol) / 3 = 0.0342 mol
The mole ratio tells us that 0.00926 moles of Aluminum (Al) react with 0.0342 moles of Copper (II) chloride.
Since Aluminum (Al) has fewer moles than Copper (II) chloride (CuCl2), Aluminum is the limiting reactant.
To determine the limiting reactant in a chemical reaction, we need to compare the amount of each reactant with their respective molar masses.
First, let's calculate the molar mass of aluminum (Al). The molar mass of aluminum is 26.98 g/mol.
Next, let's calculate the molar mass of copper (II) chloride dihydrate (CuCl2·2H2O).
The molar masses of its components are:
- Copper (Cu) = 63.55 g/mol
- Chlorine (Cl) = 35.45 g/mol
- Water (H2O) = 18.02 g/mol
Since there are two water molecules in the compound, the total molar mass of copper (II) chloride dihydrate is:
63.55 g/mol + 2 * (35.45 g/mol) + 2 * (18.02 g/mol) = 170.48 g/mol.
Now, let's calculate the number of moles for each reactant:
Moles of Aluminum (Al):
0.500 g Al * (1 mol Al / 26.98 g Al) = 0.0185 mol Al
Moles of Copper (II) chloride dihydrate (CuCl2·2H2O):
3.500 g CuCl2·2H2O * (1 mol CuCl2·2H2O / 170.48 g CuCl2·2H2O) = 0.0205 mol CuCl2·2H2O
The balanced chemical equation for the reaction between aluminum and copper (II) chloride is:
2Al + 3CuCl2 → 2AlCl3 + 3Cu
According to the stoichiometry of the reaction, we need a 2:3 molar ratio of aluminum to copper (II) chloride. This means that for every 2 moles of aluminum, we need 3 moles of copper (II) chloride.
Comparing the moles of each reactant to their stoichiometric ratio:
0.0185 mol Al / 2 mole Al = 0.00925 (0.00925 mole CuCl2 required for stoichiometric balance)
0.0205 mol CuCl2·2H2O / 3 mole CuCl2 = 0.00683 (0.00683 mole CuCl2 required for stoichiometric balance)
From the calculations, we can see that we need 0.00925 moles of CuCl2 for stoichiometric balance, but we only have 0.00683 moles available.
Therefore, the limiting reactant is copper (II) chloride (CuCl2).