Significant figures in multiplication and division

Oct 13, 2025 by wbrum.org 106 views

Understanding Significant Figures

Significant figures are an essential concept in chemistry and other scientific disciplines. They represent the precision of a measurement or calculation. When performing calculations, it's crucial to maintain the correct number of significant figures to ensure accurate results. In this article, we'll explore how to apply significant figures in calculations, using Rita's example as a case study.

Rita's Calculation

Rita wants to calculate the number of atoms in a sample by dividing Avogadro's number ( $6.02214 \times 10^{23}$ ) by 2.055. To determine the correct number of significant figures in her result, we need to analyze the given values and the calculation process.

Avogadro's Number

Avogadro's number is approximately $6.02214 \times 10^{23}$ . This value has 7 significant figures.

Divisor

The divisor is 2.055, which has 4 significant figures.

Calculation

To calculate the result, Rita will divide Avogadro's number by the divisor:

\frac{6.02214 \times 10^{23}}{2.055}

Significant Figures in the Result

When performing a division, the number of significant figures in the result is determined by the number of significant figures in the divisor. In this case, the divisor has 4 significant figures. Therefore, the result should have 4 significant figures.

Expression with Correct Significant Figures

The correct expression for Rita's result, with 4 significant figures, is:

3.00 \times 10^{23}

This expression maintains the correct number of significant figures, ensuring that Rita's calculation is accurate.

Conclusion

In conclusion, when performing calculations, it's essential to maintain the correct number of significant figures. In Rita's case, dividing Avogadro's number by 2.055 requires the result to have 4 significant figures. By following the rules of significant figures, we can ensure accurate results in our calculations.

Common Mistakes to Avoid

When working with significant figures, it's easy to make mistakes. Here are some common errors to avoid:

Rounding errors: Be careful when rounding numbers to maintain the correct number of significant figures.
Trailing zeros: Don't assume that trailing zeros are significant figures. They may be significant or not, depending on the context.
Significant figures in multiplication and division: Remember that the number of significant figures in the result is determined by the number of significant figures in the divisor or the product of the multiplicands.

By understanding and applying the rules of significant figures, you'll be able to perform accurate calculations and avoid common mistakes.

Practice Problems

To reinforce your understanding of significant figures, try the following practice problems:

Calculate the result of dividing 4.23 by 2.17, maintaining the correct number of significant figures.
Determine the number of significant figures in the result of multiplying 6.02 by 3.14.
Calculate the result of dividing 2.055 by 6.02214, maintaining the correct number of significant figures.

By practicing these problems, you'll become more comfortable with applying significant figures in calculations.

References

American Chemical Society. (n.d.). Significant Figures. Retrieved from https://www.acs.org/content/acs/en/education/resources/chemistry-in-focus/significant-figures.html
Klein, D. H. (2018). Chemistry: An Atoms First Approach. Cengage Learning.

Understanding Significant Figures: A Guide to Frequently Asked Questions

Significant figures are a fundamental concept in chemistry and other scientific disciplines. However, they can be confusing, especially when it comes to calculations and measurements. In this article, we'll address some of the most common questions and answers related to significant figures.

Q: What are significant figures?

A: Significant figures are the digits in a measurement or calculation that are known to be reliable and certain. They represent the precision of a measurement or calculation.

Q: How do I determine the number of significant figures in a measurement?

A: To determine the number of significant figures in a measurement, look for the following:

Non-zero digits: Non-zero digits are always significant figures.
Zeroes between non-zero digits: Zeroes between non-zero digits are also significant figures.
Leading zeroes: Leading zeroes are not significant figures.
Trailing zeroes: Trailing zeroes may or may not be significant figures, depending on the context.

Q: What is the rule for significant figures in multiplication and division?

A: When multiplying or dividing numbers, the number of significant figures in the result is determined by the number of significant figures in the divisor or the product of the multiplicands.

Q: How do I handle trailing zeroes in significant figures?

A: Trailing zeroes may or may not be significant figures, depending on the context. If the trailing zeroes are significant, they should be included in the count of significant figures. If the trailing zeroes are not significant, they should be ignored.

Q: What is the rule for significant figures in addition and subtraction?

A: When adding or subtracting numbers, the number of significant figures in the result is determined by the number of significant figures in the number with the fewest significant figures.

Q: Can I round numbers to the correct number of significant figures?

A: Yes, you can round numbers to the correct number of significant figures. However, be careful not to round too many times, as this can lead to errors.

Q: How do I handle decimal places in significant figures?

A: Decimal places are not significant figures. They are used to indicate the position of the decimal point.

Q: What is the difference between significant figures and decimal places?

A: Significant figures represent the precision of a measurement or calculation, while decimal places indicate the position of the decimal point.

Q: Can I use significant figures in scientific notation?

A: Yes, you can use significant figures in scientific notation. However, be careful to maintain the correct number of significant figures when converting between scientific notation and standard notation.

Q: How do I determine the number of significant figures in a calculated result?

A: To determine the number of significant figures in a calculated result, look at the number of significant figures in the numbers used in the calculation. The number of significant figures in the result should be the same as the number of significant figures in the number with the fewest significant figures.

Q: Can I use significant figures in graphing and plotting data?

A: Yes, you can use significant figures in graphing and plotting data. However, be careful to maintain the correct number of significant figures when labeling axes and plotting data.

Q: How do I handle significant figures in multiple calculations?

A: When performing multiple calculations, be careful to maintain the correct number of significant figures in each calculation. The number of significant figures in the final result should be the same as the number of significant figures in the number with the fewest significant figures.

Conclusion

Significant figures are a fundamental concept in chemistry and other scientific disciplines. By understanding the rules and guidelines for significant figures, you can ensure accurate calculations and measurements. Remember to always maintain the correct number of significant figures in your calculations and measurements.

Practice Problems

To reinforce your understanding of significant figures, try the following practice problems:

Determine the number of significant figures in the measurement 4.23 g.
Calculate the result of dividing 6.02 by 3.14, maintaining the correct number of significant figures.
Determine the number of significant figures in the calculated result of 2.055 divided by 6.02214.

By practicing these problems, you'll become more comfortable with applying significant figures in calculations and measurements.

References

American Chemical Society. (n.d.). Significant Figures. Retrieved from https://www.acs.org/content/acs/en/education/resources/chemistry-in-focus/significant-figures.html
Klein, D. H. (2018). Chemistry: An Atoms First Approach. Cengage Learning.

Note: The references provided are for informational purposes only and do not imply endorsement or affiliation with the American Chemical Society or Cengage Learning.