Expressing the Answer with Two Significant Figures

Oct 13, 2025 by wbrum.org 25 views

Understanding the Problem

The problem requires us to find the mass, in grams, of 2 moles of carbon-12 ($${ }^{12} C$$). To solve this, we need to know the molar mass of carbon-12, which is the mass of one mole of the substance.

Molar Mass of Carbon-12

The molar mass of an element is the mass of one mole of that element, expressed in grams per mole (g/mol). The atomic mass of carbon-12 is 12 u (unified atomic mass units), where 1 u is equal to 1/12 the mass of a carbon-12 atom. Therefore, the molar mass of carbon-12 is 12 g/mol.

Calculating the Mass of 2 Moles of Carbon-12

To find the mass of 2 moles of carbon-12, we can multiply the molar mass of carbon-12 by 2.

m_C = 2 × 12 g/mol = 24 g/mol

Converting Moles to Grams

Since we are asked to express the answer in grams, we need to convert moles to grams. We can do this by multiplying the number of moles by the molar mass.

m_C = 2 mol × 12 g/mol = 24 g

Expressing the Answer with Two Significant Figures

The problem asks us to express the answer using two significant figures. Therefore, we can round the answer to 20 g.

m_C = 20 g

Conclusion

The mass of 2 moles of carbon-12 is 20 grams.

Additional Information

The molar mass of an element is the mass of one mole of that element, expressed in grams per mole (g/mol).
The atomic mass of carbon-12 is 12 u (unified atomic mass units), where 1 u is equal to 1/12 the mass of a carbon-12 atom.
To find the mass of a substance, we can multiply the number of moles by the molar mass.

References

IUPAC (International Union of Pure and Applied Chemistry). (2020). Compendium of Chemical Terminology (Gold Book).
CRC Handbook of Chemistry and Physics. (2020). CRC Press.

Frequently Asked Questions

Q: What is the molar mass of carbon-12?

A: The molar mass of carbon-12 is 12 g/mol.

Q: How do I calculate the mass of 2 moles of carbon-12?

A: To calculate the mass of 2 moles of carbon-12, you can multiply the molar mass of carbon-12 by 2.

Q: What is the mass of 2 moles of carbon-12 in grams?

A: The mass of 2 moles of carbon-12 is 24 grams.

Q: How do I express the answer with two significant figures?

A: To express the answer with two significant figures, you can round the answer to 20 grams.

Q: What is the relationship between moles and grams?

A: Moles and grams are related by the molar mass of a substance. To find the mass of a substance, you can multiply the number of moles by the molar mass.

Q: What is the significance of significant figures in scientific calculations?

A: Significant figures are a way to express the precision of a measurement or calculation. In scientific calculations, it is essential to use the correct number of significant figures to ensure accurate results.

Q: Can I use the atomic mass of carbon-12 to calculate the mass of 2 moles of carbon-12?

A: Yes, you can use the atomic mass of carbon-12 to calculate the mass of 2 moles of carbon-12. The atomic mass of carbon-12 is 12 u (unified atomic mass units), where 1 u is equal to 1/12 the mass of a carbon-12 atom.

Q: What is the difference between molar mass and atomic mass?

A: The molar mass of an element is the mass of one mole of that element, expressed in grams per mole (g/mol). The atomic mass of an element is the mass of one atom of that element, expressed in unified atomic mass units (u).

Q: Can I use the molar mass of carbon-12 to calculate the mass of other substances?

A: Yes, you can use the molar mass of carbon-12 to calculate the mass of other substances. However, you need to know the molar mass of the substance you are interested in.

Additional Resources

IUPAC (International Union of Pure and Applied Chemistry). (2020). Compendium of Chemical Terminology (Gold Book).
CRC Handbook of Chemistry and Physics. (2020). CRC Press.
Khan Academy. (2020). Molar Mass.
Chemistry LibreTexts. (2020). Molar Mass.