Question

The atomic masses of two elements A and B are 30 and 90 respectively. If 'a' g of element A contains 'b' atoms, then number of atoms of B in 2a g is :

• A. $\frac{2b}{3}$
• B. $\frac{b}{3}$
• C. $\frac{b}{4}$
• D. $\frac{b}{2}$

Answer 1

The correct option is A $\frac{2b}{3}$

No. of atoms of A, $b=\left(a/30\right)N_A$

No. of atoms of B $=\left(2a/90\right)N_A=\left(2/3\right)\left(a/30\right)N_A=2b/3$

Option A is correct.