Unit+3+-+Unit+Conversions

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CONVERSIONS
Conversion Y-Chart

__ General Rules __ -To convert the different units in chemistry use the dimensional analysis - 1 mol/6.02 * 10²³ = 6.02 * 10²³ atoms/1 mol - If we multiply something by this ratio, we don’t change the value, only the unit. __ Example: __ If you have 2.5 mol of methane molecules, how many molecules do you have? 2.5 mol methane X (6.02 X10²³ molecules/1mol) = 1.51 X 10²⁴ molecules of methane

-If you are given a unit in moles, in order to convert the unit into another you must eliminate that unit. - Units are the most important thing to look at when converting. If all the units are gone except for the ones you want then you have the right answer if your calculations are correct. -Treat the mole like an algebraic variable. Mol/mol will cancel out. ^O^ to find if we need to multiply by the Avogadro's number or divide, the key is the units. If you are given a unit mole, in order to convert that unit into another you must eliminate that unit. Your known value in the numerator, therefore your conversion factor must have unit in the dominator. Mole divided by mole will cancel out, this leaves the only remaining unit

__ Mass to Mole __ [|Atomic Mass] represents the mass (gram) of 1 mole of that particular atom.

- To convert the mass to mol or vice versa we need to know the atomic mass of each element/compound used. - The mass can be found at the bottom of each atom on the periodic table. eg. H-->1.01 O-->16.00 C-->12.01 __Molecular mass__ is the mass of one molecule of that substance, we add up the atomic masses of each element to reach the molecular mass. eg. CO2= (mass of C)+ 2X( mass of O)= 12.01+2(12.01)=44.01 g/mol Al2(SO4)3=2(26.98)+3(32.07+4X16.00)=342.17 g/mol

__Example:__ 125g Pb X (1 mol / 207.20 g Pb) = 0.603 mol Pb - The grams of Pb cancel out leaving only moles in the answer. - There can be more than one step needed to calculate the mass. - You have to convert to moles first before converting to grams.

__ Example: __ convert 265 atoms of H -->g 265 atoms H X (1 mol H /6.02X10²³ atoms H) X (1.01g H / 1 mol H)=4.45X10-²²g H

__Example:__ convert 1.24X10 ¹⁹ --> mol of He 1.24X10 ¹⁹ He atoms X 1 mol He/ 6.02X1023 =2.06X10(- ⁵ )

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