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Significant figures help for chem

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skierdfd
Posts: 20 - Karma: 37
so i need help with this lab if i have:

2 grams of a mixture (iron, sand, salt) and im trying to find the percent mass for iron which has a mass of .45 g do i divide the .45 g into 2 g to get .225 grams timed by 100 percent to get what?

basically i dont know what to get for an answer as far as 20 being reduced to have only 1 sig fig
Oct 25 2010 10:37PM
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the_moderaper
Posts: 2465 - Karma: 218
20 is one sigfig. no decimal means start from the right, skip all the 0's and then count all numbers as sigfigs
Oct 25 2010 10:40PM
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PeteySkeety
Posts: 996 - Karma: 209
.
Oct 25 2010 10:41PM
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MCIRONCOCK
Posts: 3094 - Karma: 30
When determining significant figures, you should always start from the left and select numbers based on their importance. Prime numbers, square roots, important dates in history; these are all significant figures and you should include them in your final answers.
Oct 25 2010 10:45PM
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skierdfd
Posts: 20 - Karma: 37
wow my dad is a chem teacher and he just said the completley wrong thing to me no joke. well maybe cus hes currently smoking out of a bowl....

oh well

thanks guys!!!!!!
Oct 25 2010 10:46PM
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a_pla5tic_bag
Posts: 9210 - Karma: 5,357
another easy way to figure it out is to convert the number to scientific notation, that will give you the sig figs.

they retaught us all of this in like the first lecture in chem this year.
Oct 25 2010 10:47PM
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50in07
Posts: 3070 - Karma: 1,471
I remember doing that. But dont remember how.
Oct 25 2010 10:47PM
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1337
Posts: 31038 - Karma: 29,003
20% is correct.


I remember my first year of chem...
Oct 25 2010 10:51PM
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Gstrong
Posts: 4776 - Karma: 518
Click for larger image
Oct 25 2010 10:51PM
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the.cheat
Posts: 2859 - Karma: 171
i slept all the days of sig figs then i went like a month doing them all wrong. then i figured it out. i still dont get why i have to do it though
Oct 25 2010 10:54PM
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a_pla5tic_bag
Posts: 9210 - Karma: 5,357
i see why it's used, but it's stupid a lot of the times. you get an answer thats like 2434 and it's like only 1 sig fig so now you answer is 2000. 2000 and 2434 are pretty different numbers if you were actually using them for something.
Oct 26 2010 9:43AM
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the_king
Posts: 55 - Karma: 25
Really nice du, +K for sheezy playah
Oct 26 2010 10:10AM
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