# Worksheet: Relative Atomic Mass

In this worksheet, we will practice calculating the relative isotopic abundance of elements and using these data to calculate their relative atomic masses.

**Q1: **

The atomic mass unit (u) is defined as th of the mass of an atom of carbon-12. What is the mass of a carbon-13 atom in atomic mass units, to 2 significant figures?

**Q2: **

The atomic mass unit (u) is defined as th of the mass of an atom of carbon-12. What is the mass of a silicon-30 atom in atomic mass units?

**Q3: **

The atomic mass unit (u) is defined as th of the mass of an atom of carbon-12. What is the mass of a fluorine-19 atom in atomic mass units?

**Q4: **

The relative atomic mass of an element is the average mass of one atom on a scale .

- Awhere the most common isotope of the element has a mass of 100
- Bfrom 0–100, where 0 is the mass of hydrogen and 100 is the mass of the heaviest element
- Cwhere hydrogen-1 has a mass of 1
- Dwhere carbon-12 has a mass of 12

**Q5: **

Relative isotopic mass is the mass of an isotope of an element on a scale .

- Awhere the most common isotope of the element has a mass of 100
- Bwhere carbon-12 has a mass of 12
- Cfrom 0–100, where 0 is the mass of hydrogen and 100 is the mass of the heaviest element
- Dwhere hydrogen-1 has a mass of 1

**Q6: **

As a molar percentage, 80.3% of a boron sample is and the remainder is . What is the average molar mass of the boron sample?

**Q7: **

Chlorine has two stable isotopes, chlorine-35 and chlorine-37. A sample of chlorine was analyzed using a mass spectrometer, and the following isotopic abundances were calculated.

Isotope | Chlorine-35 | Chlorine-37 |
---|---|---|

Abundance (mol %) | 75.8% | 24.2% |

What is the relative atomic mass of chlorine in the sample?