Week 3 Lectures - Chem 139

# Week 3 Lectures - Chem 139 - 1 Sig Figs in Calculated...

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Unformatted text preview: 1 Sig Figs in Calculated Values • Since there is a limit to the accuracy of measured values, there must also be a limit to the accuracy of calculations performed using measured values. • In general, we can say that a calculated value can be no more accurate than the least accurate measurement used in the calculation. • However, exactly how the least-accurate measurement determines the number of significant figures in the calculated result depends on the operation performed. 2 Sig Figs in Calculated Values (cont) • Multiplication/Division : The result of a multiplication or division must have the same number of significant figures as the measurement with the fewest number of significant figures . • For example, let's say you want to determine the area of a rectangular room using the lengths of two walls, 3.55 m and 11.65 m: • Reporting 41.3575 m 2 implies that the calculated area was more accurate than either of the wall measurements, which is impossible. • Since your least accurate value has two certain digits and one estimated digit, your calculated digit simply can't do any better, so it cannot have more than three significant figures . 2 2 measured value measured value correct answer calculator answer 3 sig figs 4 sig figs 3 sig figs 6 digits 3.55 m 11.65 m 41.3575 m 41.4 m × = = 1 2 3 142 43 142 43 1 442 4 43 3 Sig Figs in Calculated Values (cont) • Multiplication/Division : The result of a multiplication or division must have the same number of significant figures as the measurement with the fewest number of significant figures . • For example, let's say you want to determine the area of a rectangular room using the lengths of two walls, 3.55 m and 11.65 m: • Reporting 41.3575 m 2 implies that the calculated area was more accurate than either of the wall measurements, which is impossible....
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Week 3 Lectures - Chem 139 - 1 Sig Figs in Calculated...

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