Question

What is the expected mass (in kg) of a 10 over 5 B isotope? 1 proton = 1.6726 × 10-27 kg 1 neutron = 1.6749 × 10-27 kg A.1.67 × 10-26 kg B.1.67 × 1026 kg C.2.51 × 10-26 kg D.2.51 × 1026 kg

Answer 1

$^{10}_5 B$
An atom of this isotope contains 5 protons and 10-5=5 neutrons.

$5 \times 1.6726 \times 10^{-27} + 5 \times 1.6749 \times 10^{-27} = \\ 8.363 \times 10^{-27} + 8.3745 \times 10^{-27}= \\ 16.7375 \times 10^{-27}= \\ 1.67375 \times 10^{-26} \approx \\ 1.67 \times 10^{-26}$

The answer is A. 1.67 × 10⁻²⁶ kg.