Question

qe 5. what is the average atomic mass of neon, if there are 175 atoms of the 200 atom sample whose mass is 20 amu and the rest have a mass of 22 amu.
qa 20.3 amu
qa 22.2 amu
qa 21.0 amu
qa 22.0 amu
clear all

Explanation:

Step1: Find number of atoms with mass 22 amu

Assume total number of atoms is 200. Number of atoms with mass 22 amu is $200 - 175= 25$.

Step2: Calculate total mass

Total mass = (mass of 20 - amu atoms×number of 20 - amu atoms)+(mass of 22 - amu atoms×number of 22 - amu atoms). So, total mass = $(20\times175)+(22\times25)=3500 + 550=4050$ amu.

Step3: Calculate average atomic mass

Average atomic mass = $\frac{\text{total mass}}{\text{total number of atoms}}=\frac{4050}{200}=20.25\approx20.3$ amu.

Answer:

20.3 amu