Question

How many moles of lead $(II)$ chloride will be formed from a reaction between $6.5g$ of $PbO$ and $3.2g$ of $HCl$? (Atomic weight of $Pb=207$)
$PbO+2HCl\to PbC{{l}_{2}}+{{H}_{2}}O$
A. $0.011$
B. $0.029$
C. $0.044$
D. $0.333$

Answer 1

Mole concept gives the relationship between the number of moles, weight and molar mass of the compound. A mole is used to calculate the values of atoms and molecules. The molar mass of a compound is calculated by adding up the atomic masses of the elements bound in the molecule multiplying each with their number of atoms in the molecule.

Formula used:
$n=\dfrac{W}{M}$
where, $n$ is the number of moles, $W$ is the weight and $M$ is the molar mass.

Complete step by step answer:
Here, it is given that the weight of $PbO$ is $6.5g$,
Weight of $HCl$ is $3.2g$
Let us write the balanced chemical reaction:
$PbO+2HCl\to PbC{{l}_{2}}+{{H}_{2}}O$
The number of moles is calculated by mole concept as follows:
$n=\dfrac{W}{M}$
where, $n$ is the number of moles, $W$ is the weight and $M$ is the molar mass.
Substituting the values in above formula, we get,
The number of moles of lead oxide $=\dfrac{6.5}{223}=0.029$
The number of moles of hydrogen chloride $=\dfrac{3.2}{36.5}=0.087$
Now, we will calculate the ratio of moles given and stoichiometry.
$PbO=\dfrac{0.029}{1}=0.029$
$HCl=\dfrac{0.087}{2}=0.0435$
As you can see the ratio of $PbO$ , that is, $0.029$ is lower than the ratio of $HCl$ , that is, $0.0435$. Therefore, $PbO$ is the limiting agent and the product will form on the basis of the number of moles of $PbO$ .
Hence, the moles produced of $PbC{{l}_{2}}=\dfrac{1}{1}\times 0.029=0.029\,moles$ .

So, the correct answer is Option B.

Additional information:
Mole is defined as a scientific unit which is used to measure large quantities of atoms and molecules. It is defined as the amount of substance present in a sample.
$1\,mole=6.022\times {{10}^{23}}$ particles. This number is also called Avogadro's number $({{N}_{A}})$ .Molar mass is defined as the addition of atomic mass of atoms, combined in a molecule. Here, the molar mass of $PbO$ is $223$ and molar mass of $HCl$ is $36.5$ .
Moles are defined as the weight of the compound per molar mass of the compound.
Formula mass is different from molecular mass. In formula mass, there is an addition of atomic masses of ions present in an ionic compound, whereas molecular mass is the addition of atomic masses of the atoms in a molecule.

Note: Limiting reagent is a reactant that gets completely consumed when a chemical reaction gets completed and so the amount of product formed depends upon the quantity of the limiting reagent.
Molar mass is calculated in gram per mole by the addition of atomic masses in a molecule.