Ch.1 - Chemical Tools: Experimentation & Measurement

McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook

McMurry 8th Edition

Ch.1 - Chemical Tools: Experimentation & Measurement

Problem 90b

Chapter 1, Problem 90b

Round off the following quantities to the number of signifi-cant figures indicated in parentheses. (b) 68.507 g (2, 3)

Verified step by step guidance

Identify the number of significant figures required: 2 and 3.

For 2 significant figures, look at the first two digits of 68.507, which are 6 and 8.

Check the third digit (5) to determine if rounding is necessary. Since it is 5 or greater, round up the second digit.

For 3 significant figures, look at the first three digits of 68.507, which are 6, 8, and 5.

Check the fourth digit (0) to determine if rounding is necessary. Since it is less than 5, do not round up the third digit.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Significant Figures

Significant figures are the digits in a number that contribute to its precision. This includes all non-zero digits, any zeros between significant digits, and trailing zeros in the decimal portion. Understanding significant figures is crucial for accurately reporting measurements and ensuring that calculations reflect the precision of the data.

Rounding Rules

Rounding rules dictate how to adjust numbers to the desired level of precision. When rounding, if the digit to the right of the last significant figure is less than 5, the last significant figure remains unchanged. If it is 5 or greater, the last significant figure is increased by one. These rules help maintain the integrity of the data while conforming to the specified number of significant figures.

Measurement Precision

Measurement precision refers to the degree of reproducibility of a measurement, which is often indicated by the number of significant figures. A measurement with more significant figures suggests a higher precision, while fewer significant figures indicate less precision. Understanding this concept is essential for interpreting data and making informed conclusions in scientific contexts.

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Round off the following quantities to the number of significant figures indicated in parentheses. (a) 35,670.06 m (4, 6)

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Textbook Question

The diameter of the Earth at the equator is 7926.381 mi. (a) Round off this quantity to four significant figures and then to two significant figures.

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