Question

The atomic masses of two elements $P$ and $Q$ are $20$ and $40$, respectively. If ${}^{\prime }{a}^{\prime }g$ of $P$ contains ${}^{\prime }{b}^{\prime }$ atoms, how many atoms are present in ${}^{\prime }2a^{\prime }g$ of $Q$?

• A. $a$
• B. $b$
• C. $2a$
• D. $2b$

Answer 1

Answer: (B)

$b$

Atomic mass

$P=20$

$P=\frac{w}{M}\times N_A=\frac{a}{20}\times N_A=b---\left(1\right)$

$Q=40$

$Q=\frac{2a}{40}\times N_A=X$

$Q=\frac{a}{20}\times N_A=X$

From equation $\left(1\right);\frac{a}{20}\times N_A=b$

$\therefore X=b$

$\therefore 2agm$ of $Q$ contains $b$ atom

Ans is option $b$.