# Question #0137a

##### 1 Answer

#### Answer:

Using your ratio gives the mass of

#### Explanation:

Let's let

The average atomic mass is the **weighted average** of the isotopic masses.

You multiply each isotopic mass by its relative abundance (percentage as a decimal fraction) in the mixture.

Thus,

Now,

So,

∴

**Using the correct mass ratio**

Your ratio of the two atomic masses is **incorrect**.

The correct ratio is 1.0253.

Using this number, we get

∴