Question

what is the average mass of carbon, if there is 97% c - 12, 2% c - 13, and 1% c - 14?
a (97)(12)+(2)(13)+(1)(14)=1204
b (0.97)(12)+(0.02)(13)+(0.01)(14)=12.04
c (97)(12)+(0.02)(13)+(0.01)(14)=1164.4
d (0.97)(12)+(0.2)(13)+(0.01)(14)=14.38

Explanation:

Step1: Convert percentages to decimals

Percentages are converted to decimal - form for calculation. 97% becomes 0.97, 2% becomes 0.02 and 1% becomes 0.01.

Step2: Calculate the weighted - average

The average mass of carbon is calculated using the formula for weighted - average: \((0.97\times12)+(0.02\times13)+(0.01\times14)\).
First, \(0.97\times12 = 11.64\).
Second, \(0.02\times13=0.26\).
Third, \(0.01\times14 = 0.14\).
Then, \(11.64 + 0.26+0.14=12.04\).

Answer:

B. \((0.97)(12)+(0.02)(13)+(0.01)(14)=12.04\)