Your turn

Recall seeing these values on the previous page. Now, you will have the chance to practice calculations using atomic weight intervals and conventional atomic weight values.

Element | Atomic Weight (Interval) | Conventional Atomic Weight |
---|---|---|

Carbon | [12.0096, 12.0116] | 12.011 |

Hydrogen | [1.007 84, 1.008 11] | 1.008 |

1) You are given a sample of methane (CH_{4}), and are asked to calculate its molecular weight. What value do you calculate as the molecular weight for a sample of methane with an unknown isotopic composition and unknown source?

- 49.048
- 16.043
- 16.040
- 16.042

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The correct answer is B. This answer was calculated with the conventional atomic weight numbers given above.

Remember - to calculate the molecular weight of a molecular made of atoms with an unknown isotopic composition or unknown source, it is important to use the conventional atomic weight values. Using the mean values of the intervals is not correct.