Calculate the number of moles of excess reactant that will be left-over when .350 g if HCN react with .500 g of 02:
HCN+O2->N2+CO2+H20
Balance the equation before you do anything.
mols HCN = grams/molar mass
mols O2 = grams/molar mass.
Determine which is the limiting reagent. Do that by converting mols HCN to mols CO2 using the coefficients in the BALANCED equation. Do the same for mols O2 to mols CO2. It is likely that the two values will not agree which means one of them is wrong. The correct value in limiting reagent problems is ALWAYS the smaller value and the reagent responsible for this lower value is the limiting reagent.
Finally, convert mols of the limiting reagent to mols of the excess reagent, convert that to grams excess reagent (the amount used), subtract from the initial amount to find the amount left over.
To determine the number of moles of excess reactant left over, we first need to identify the limiting reactant. The limiting reactant is the reactant that is completely consumed in the reaction, determining the maximum amount of product that can be formed.
Let's calculate the number of moles for both reactants:
Molar mass of HCN:
M(H) = 1.01 g/mol
M(C) = 12.01 g/mol
M(N) = 14.01 g/mol
Molar mass of HCN = (1.01 + 12.01 + 14.01) g/mol = 27.03 g/mol
Number of moles of HCN = mass of HCN / molar mass of HCN
Number of moles of HCN = 0.350 g / 27.03 g/mol ≈ 0.01292 mol of HCN
Molar mass of O2:
M(O) = 16.00 g/mol
Number of moles of O2 = mass of O2 / molar mass of O2
Number of moles of O2 = 0.500 g / 32.00 g/mol ≈ 0.01563 mol of O2
From the balanced chemical equation, the stoichiometric ratio between HCN and O2 is 1:1. Therefore, the number of moles of HCN and O2 are equal.
Since the stoichiometry of the reaction shows that both HCN and O2 react in a 1:1 ratio, there is no excess reactant. Thus, no moles of excess reactant will be left over.
To calculate the number of moles of excess reactant that will be left over, we first need to identify the limiting reactant. The limiting reactant is the reactant that is completely consumed in a reaction and determines the maximum amount of product that can be formed.
To find the limiting reactant, we need to compare the number of moles of each reactant to the stoichiometry of the reaction. The stoichiometry of the reaction is given by the balanced equation:
HCN + O2 -> N2 + CO2 + H2O
From the equation, we can see that the molar ratio of HCN to O2 is 1:1. This means that for every 1 mole of HCN, we need 1 mole of O2.
Let's calculate the number of moles for each reactant:
Moles of HCN = Mass of HCN / molar mass of HCN
Molar mass of HCN = 1.007 + 12.01 + 14.01 = 27.02 g/mol
Moles of HCN = 0.350 g / 27.02 g/mol = 0.0129 mol
Moles of O2 = Mass of O2 / molar mass of O2
Molar mass of O2 = 16.00 + 16.00 = 32.00 g/mol
Moles of O2 = 0.500 g / 32.00 g/mol = 0.0156 mol
Now, we compare the moles of each reactant to determine the limiting reactant:
The molar ratio of HCN to O2 is 1:1, so they have the same number of moles. Therefore, there is enough of each reactant present to completely react, and there will be no excess reactant left-over.
In this case, both reactants are completely consumed in the reaction, and there is no excess reactant left over.