Question

Calculate number of neutrons present in 12x10^25 atoms Of oxygen (80^17) :
(Given: NA = 6x 10^23)
(a) 1800
(b) 1600
(C) 1800 NA
(d) 3200 NA

Answer 1

Solution: The answer is $1800N_A$ . i.e option C.

Atomic number $=P=8$ .

Atomic Mass $= N+P = 17.$

Therefore $N = 9,$ Which is number of neutrons.

Total number of neutrons in $12\times10^{25} atoms = 9\times 12\times 10^{25}=\frac{9\times12\times10^{25}\times N_A}{6\times10^{23}}$

$=1800N_A$ .