Question

How do you convert $64.3g$ of $PbB{r_2}$ to moles?

Answer 1

Hint: We know that in chemistry we study about various elements, their physical and chemical properties, their nature and reactivity with other elements. Also, we know that substance or a matter has some mass. Elements also have mass. And each element has a unique atomic mass or so-called molar mass. Molar mass is the mass of a chemical compound or element divided by the amount of sample in that substance (in moles). For example, oxygen has an atomic number $18$ and its moles mass is $36gm$.

Complete step by step answer:
The given compound for which we need to find the number of moles is $PbB{r_2}$- Lead (II) bromide. Physically it is a white colored powder that is produced in the burning of leaded gasolines.
For elements, we have predefined or readily measured molar mass.
In the given compound there are two elements present. We have one lead atom bonded with two bromine atoms.
We know the molar mass of lead is $207gm/mol$ and the molar mass of bromine is $79.90gm/mol$.
Thus, the molar mass of $PbB{r_2}$ can be calculated as-
$207 + 2 \times 79.90$
On simplification we get
$ = 366.8gm/mol$
To calculate moles, we have a formula. Moles is calculated as the total mass of a substance divided by the molar mass of the substance.
Thus,
$n = \dfrac{{64.3}}{{366.8}}$
On division we get,
$n = 0.175$
Thus, there are $0.175$ moles of $PbB{r_2}$ in $64.3g$ of $PbB{r_2}$.

Note:
As we know that the mole concept is the easiest and the most efficient measure to calculate the moles of a substance or even to calculate the concentration or mass of a substance. In mole concept there are various terminologies like molarity, molality, normality, concentration, moles, molar mass, molecular mass, etc. All these terms are used in measure of substance in any composition or mixture. Mole concept gives the accurate measure of the elements involved in a reaction.