Question

A compound has empirical formula as A2B and has molecular mass of 120 u (Atomic mass of A = 10 amu and B = 20 amu). Then the number of A atoms in each molecule of the compound is​

Answer 1

Need to FinD :-

• The number of A atoms in each molecule of the compound .

$\red{\frak{Given}}\begin{cases}\textsf{ A compound has empirical formula as A _{\sf 2} B.}\\\textsf{ It has a molecular mass of 120 u.}\\\textsf{ At. mass of A = 10 amu and At. mass of B = 20 amu. }\end{cases}$

• By Question :-

$\sf \to Emipirical \ Formula \ = \ \red{A_2B}$

• We have :-

• Atomic mass of A = 10 amu
• Atomic mass of B = 20 amu
• Molecular weight = 120 amu

$\sf \to Emipirical \ Formula \ Wt. \ = \ 10(2)+20 amu = \red{40\ amu} .$

$\rule{200}2$

• Also we know that :-

$\dashrightarrow \sf n =\dfrac{Molecular\ wt.}{Empirical\ Formula\ wt.}\\\\\sf\dashrightarrow n =\dfrac{120u}{40u} \\\\\sf\dashrightarrow \boxed{\pink{\sf n =3 }}$

$\rule{200}2$

• Therefore the Compound is :-

$\sf\to (A_2B)_n \\\\\sf\to (A_2B)_3 \\\\\sf\to (A_{((2)(3)} B_3 ) \\\\\sf\to \boxed{\pink{\sf A_6B_3 }}$

• Therefore the Number of atoms of A in the Molecule of the Original Compound is 6

$\rule{200}2$