1. The correct answer for the product (6.45 × 105) × (1.2 × 104) is: (considerin

Question

1. The correct answer for the product (6.45 × 105) × (1.2 × 104) is: (considering significant figures) A. 7.7 × 109 B. 5.375 × 101 C. 7.74 × 109 D. 7.7 × 1011 E. 7.74 × 1011

2. The correct answer for the product (8.2 × 10-3) × (2.84 × 105) is: (considering significant figures) A. 2.3288 × 103 B. 2.3 × 103   C. 2.3 × 104   D. 2.3 × 105 E. 2.33 × 102

3. A bottle of liquid mercury has a mass of 5.00 × 102 g. What is the volume of the mercury in mL? (density mercury = 13.6 g/mL) A. 36.8 mls B. 25.3 mls C. 104.6 mls D. 9.22 mls E. 29.44 mls

4. A 19.0-g sample of lithium is completely burned in air to form lithium oxide. The mass of lithium oxide must be

A. less than 19.0 g. B. greater than 19.0 g. C. equal to 19.0 g. D. all of the above. E. none of the above.

Explanation / Answer

1)  (6.45 × 10^5) × (1.2 × 10^4) =  7.7 × 10^9

answer : A) 7.7 × 10^9

2) (8.2 × 10-3) × (2.84 × 105) =  2.3 × 10^3

answer : B). 2.3 × 10^3

explanation : In multiplication and division, the number of significant figures in the final product or quotient is determined by the original number that has the smallest number of significant figures

3) density = mass / volume

13.6 = 5.00 x 10^2 / volume

volume = 36.76 mL

but signifants should be 3 so

answert : A) 36.8 mL

4 )

4 Li + O2 -----------------------> 2 Li2O

28 g 60 g

19 g 40.7 g

answer :  B. greater than 19.0 g

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