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Significant Figures “Sig Figs ”. Atlantic-Pacific Rule. Atlantic-Pacific Rule. Decimal P resent – P acific Decimal A bsent – A tlantic. Ex. 1.250 g. 1 2 3 4 4 Sig Figs. Start on the Pacific (left side) with the 1 st non-zero & count to the end. Ex. 12500 g.
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Significant Figures“Sig Figs” Atlantic-Pacific Rule
Atlantic-Pacific Rule Decimal Present – Pacific Decimal Absent – Atlantic Ex. 1.250 g 1 2 3 4 4 Sig Figs Start on the Pacific (left side) with the 1st non-zero & count to the end Ex. 12500 g 3 2 1 3 Sig Figs Start on the Atlantic (right side) with the 1st non-zero & count to the end Pacific Atlantic
Examples: Counting Sig Figs • 520 mL • decimal absent start from the Atlantic (right side) with the 1st non-zero and count to the end • 2 Sig figs • 0.0102 ms • decimal present start from the Pacific (left side) with the 1st non-zero and count to the end • 3 sig figs • 0.230 kg —3 sig figs • 25 600 L —3 sig figs
Rules for Adding/Subtracting with Sig Figs • The answer to an addition or subtraction problem must have the same number of decimal places as the measurement with the least number of decimal places. • Examples: • 1.3453g + 3.2g (the measurement with the least # of decimal places is 3.2g. It has 1 decimal place, so the answer must have just 1 decimal place) • Answer: 4.5 g • 5.73mL – 6.3456mL (5.73 has 2 decimal places) • Answer: -0.62mL (our answer needs 2 decimal places) • 3.333s + 2.22s + 1.1s • Answer: 6.7 s
Multiplying/Dividing with Sig Figs • The answer to an multiplication or division problem must have the same number of Sig Figs as the measurement with the least number of Sig Figs. • Examples: • 0.3287 g x 45.2 g (45.2 has the least number of sig figs—it has 3 sig figs. So, our answer needs 3 sig figs. • Answer: 14.9 g • 0.258 mL ÷ 0.36105 mL (0.258 has the least # of sig figs—it has 3. So, our answer needs 3 sig figs) • Answer: 0.715 mL