HELP PLEASE with Chem/Math?!
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HELP PLEASE with Chem/Math?!

[From: ] [author: ] [Date: 11-09-13] [Hit: ]
000001, but I need help with the correct number of Sig.2.) (6.5785 x 10^4) (3.I got the answer as 2153.......
Perform each of the following calculations using scientific notation. Make sure each answer in scientific notation to the proper number of significant digits.

1.) (5.10 x 10^-4) (2.843 x 10^-3)
I got the answer as: 0.000001, but I need help with the correct number of Sig. figures

2.) (6.5785 x 10^4) (3.27410 x 10^-2)
I got the answer as 2153.87 but again, I need help with SF

3.) (7.001 x 10^-14) (6.800 x 10^-43)
I got the answer as 4.76068E^-56 .... what does E mean? and what are the correct number of SF?

4.) (2.561 x 10^-17) (6.8009 x 10^-45) / (7.06 x 10^16) (4.50 x 10^20)
I got 1.11016E^-57 ... again, what is E and what are the correct number of figures?

5.) (8.7 x 10^-26) (3.456 x 10^-54) / (3.56 x 10^-78) (7.787 x 10^2)
I got 65.7678 ... is that right? with the significant figures?

Please help me....I don't understand significant figures. THANKS SO MUCH!

-
1.) Since you are multiplying, you count the sig. figs. and the one with the least is the amount you use!
(5.10 x 10^-4): This has 3 sig. fig. the 5, 1, and 0
(2.843 x 10^-3): This has 4 sig. fig. the 2, 8, 4, and 3
You don't need to count the 10^n
The answer is 1.44993 x 10^-6
So the least sig. fig. is 3 so the answer should be 1.45 x 10^-6

2.) All these Qs are multiplying so same rule!
(6.5785 x 10^4): 5 sig. figs. (6, 5, 7, 8, and 5)
(3.27410 x 10^-2): 6 sig. figs. (3, 2, 7, 4, 1, and 0)
So you need 5 in your answer.
2153.87 --> 2153.9
Since you want the answer in scientific notation, you need to move the decimal to the right. The answer will be 2.1539 X 10^3

3.) The E means the power of 10. So when it says E^-56, it means 10^-56
(7.001 x 10^-14): 4 sig. figs.
(6.800 x 10^-43): 4 sig. figs.
4.76068E^-56 --> 4.761 x 10^-56

4.) The rule for dividing is the same as for multiplying!
(2.561 x 10^-17): 4 sf
(6.8009 x 10^-45): 5 sf
(7.06 x 10^16): 3 sf
(4.50 x 10^20): 3 sf
1.11016E^-57 --> 1.11 x 10^-57


5.) (8.7 x 10^-26): 2 sf
(3.456 x 10^-54): 4 sf
(3.56 x 10^-78): 3 sf
(7.787 x 10^2): 4 sf
65.7678 --> 66
Answer in scientific notation will be 6.6 x 10^1


Sorry about such a long post! I don't know whether you don't know how to count the sig. fig. or use scientific notation or whatever your question was really about. I suggest you read your textbook about sig. fig. rules because that helped me a lot :)
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