Question

If a copper – containing compound contains $4.999$by mass and there are $2$copper atoms per formula unit, what is the molar mass of the compound?

A) $2547g/mol$
B) $47.50g/mol$
C) $31.75g/mol$
D) $1274g/mol$

Answer 1

Hint : In order to solve this question first determine the number of atoms per formula unit. Then we would multiply the atomic weight of elements with its atomic number.

Complete step-by-step solution:
let us assume the molar mass of compound =$$$$M
According to the question there are two Copper atoms in $1mole$of atom i.e. $128gms$ of atom,
Here, copper mass is given $4.999$
Now, we will calculate the molar mass of the compound-

& \Rightarrow \left( \dfrac{4.999}{100} \right)\times M=128gms \\\ & \Rightarrow M=\dfrac{12800}{4.99}=2547g/mol \\\ \end{aligned}$$ **So, the right option is a) $$2547g/mol$$.** **Note:** Italian physicist Amedeo Avogadro found the concept of molar mass. Molar mass is mainly used to convert a mass to an amount of substance that is expressed as atoms, molecules, and the ions. $$%$$of copper) $$\times $$Molar mass $$=$$Mass of copper