Methods and Tools of Chemistry

1. Methods and Tools of Chemistry Chapter 2 Science Department Corpus Christi School

2. Measurement Certain digits uncertain digit 2.35cm

3. Example 1 The volume of a sample of sodium chloride solution is 19.80 mL.Which is the uncertain digit in the recorded volume of the sample?

4. Example 2 Which of the following represents the mass of sodium chloride with ' 5 ' as a uncertain digit? 5.246g 2.546g 5.245g

5. Example 3 The mass of a sample of salt is found to be 6.3912 g, 6.4003 g, and 6.3941 g in the first, second, and third trail respectively. What is the uncertain digit in each trial? 1, 0, 4 c. 2, 3, 1 3, 4, 3 d. 6, 6, 6

6. Significant Figures RULE 1: All nonzero digits are significant Examples: 3.2cm – two sig. fig. 1.45m – three sig. fig 2.216g – four sig fig.

7. Significant Figures RULE 2: Zeros in between nonzero digits are significant Examples: 3.o2cm – three sig. fig. 1.405m – four sig. fig 2.2016g – five sig fig.

8. Significant Figures RULE 3: Zeros at the right of the decimal point and at the right of the nonzero digits are significant Examples: 3.20 cm – three sig. fig. 1.450 m – four sig. fig 2.0 g – two sig fig.

9. Significant Figures RULE 4: Zeros at the right of the decimal point but at the left of nonzeros that are written only to indicate the decimal place are not significant Examples: 0.32 cm – two sig. fig. 0.0145m – three sig. fig 0.002216g – four sig fig.

10. Significant Figures RULE 5: For whole numbers, zeros after nonzero digits are not significant unless a decimal point or a bar on top of zero is placed to indicate the zero, or all zeros including such zero with a barline are significant Examples: 10 cm – one sig. fig. 100.0 m – four sig. fig 1000 g – four sig fig.

11. Exercises 0.0803 mg 678.3 kg 3 450. 000 L 6500.7 ft 0.00545 lb 22 450 000 oz 70.5230 in

12. Exercises 21.0803 mg 608.30 kg 350 00.0 L 6500.70 ft 5 000lb