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Use of appropriate significant figures General Chemistry

All non-zero digits are significant. 1345 = 4 sig figs 3489.33 = 6 sig figs 987583.3456 = 10 sig figs

Zeros between non-zero digits are significant. 1003002 = 7 sig figs 1000000004 = 10 sig figs 102 = 3 sig figs

Zeros to the left of the first non-zero digit are not significant. O.322 = 3 sig figs 0.0000897 = 3 sig figs 0.008009 = 4 sig figs

If a number ends in zeros to the right of the decimal point, those zeros are significant. 323.200 = 6 sig figs (great accuracy by a device) 65.20 = 4 sig figs 75.0 = 3 sig figs

Sig figs and scientific notation: All numbers before the exponent are significant 3.0060 x 10 8 = 5 sig figs, do not count the full extended number 7.05 x 10 -12 = 3 sig figs 3.00987 x 10 4 = 6 sig figs

If a number ends in zeros to the left of the decimal point, those zeros may or may not be significant. From dartmouth.edu: If we make a statement that the weight of an object is 120 g, how do we convey our knowledge of whether the balance was accurate to ± 1 g or ± 10 g? Answer: The ambiguity can be removed by using exponential notation. The weight can be expressed as 12. x 10 1 g or 1.2 x 10 2 g if we wish to quote unambiguously to 2 sig figs, and 12.0 x 10 1 g or 1.20 x 10 2 g if we have a confidence level extending to 3 sig figs. Note: We cannot write 120.0 g since this requires known accuracy of ± 0.1 g.

Multiplication or Division: the result can have no more sig figs than the least accurate number. 12.897 x 58.30 = 751.9 67.3/23.457 = 2.87 Explain these answers

Addition or Subtraction: the result must be reported to the same number of decimal places as the number with the fewest decimal places. 12.7 + 13.987 + 32. = 59. 145.68 - 32.4 = 113.3 Explain these answers

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