document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1208781>Question 1208781</A>: <I><SPAN STYLE=\"word-break: break-all;\"> An iron atom has a mass of 1.79 × 10^−22 grams. A sample of iron has a mass of 9. 129 × 10^−3 grams?\r<BR>\n" );
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document.write( "Determine how many atoms are in the sample using scientific notation.<BR>\n" );
document.write( "a. 7.339 × 10^−25<BR>\n" );
document.write( "b. 7.339 × 10^20<BR>\n" );
document.write( "c. 5.1 × 10^19<BR>\n" );
document.write( "d. 5.1 × 10^−24 </SPAN>\n" );
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document.write( "Answer: <font color=red>C)  5.1 x 10^19</font>\r<BR>\n" );
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document.write( "Work Shown\r<BR>\n" );
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document.write( "n = number of atoms<BR>\n" );
document.write( "(atom's weight)*(number of atoms) = total weight<BR>\n" );
document.write( "(atom's weight)*(n) = total weight<BR>\n" );
document.write( "n = (total weight)/(atom's weight)<BR>\n" );
document.write( "n = 9.129 x 10^(-3) divide 1.79 x 10^(-22)<BR>\n" );
document.write( "n = (9.129/1.79) x 10^(-3 - (-22) )<BR>\n" );
document.write( "n = 5.1 x 10^(-3+22)<BR>\n" );
document.write( "n = <font color=red>5.1 x 10^19</font>\r<BR>\n" );
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document.write( "If you don't have your calculator with you, or you're in a hurry, then you can take advantage of the fact there is multiple choice. <BR>\n" );
document.write( "Focus on the 10^(-3) dividing over 10^(-22). As shown above, that evaluates to 10^19 which is present in <font color=red>choice C</font> only. We can rule out the other options and don't need to calculate the 5.1\r<BR>\n" );
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document.write( "Another thing to notice:<BR>\n" );
document.write( "9.129 is close to 10<BR>\n" );
document.write( "1.79 is close to 2<BR>\n" );
document.write( "10/2 = 5 which is close to 5.1<BR>\n" );
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