A NaCl crystal has a mass of 0.15mg. how many moles of Na^+ are present in the crystal. ( express the answer to two significant figures and include the appropriate units) . How many Na^+ ions are present? ( express the answer using two significant figures)
First Step: Convert 0.15 mg into grams. 0.15 mg / 1000 mg = 0.00015 g NaCl.
Second Step: convert it into moles. 0.00015 g NaCl
/ 58.44 g NaCl = 2.5*10-6 moles NaCl ( By using
formulae: no of moles= mass/molar
mass)
Third Step: convert it into Na+ ions by setting
conversion factor: 2.5*10-6 moles NaCl x (1 mol Na+ ions
/ 1 mol NaCl) = 2.5*10^-6 moles Na+ ions.
Fourth Step: for the Na+ ions present, all you
have to do is convert it using avogadro number.
So, set up conversion factor 2.5*10-6 moles Na+ ions x
(6.022*1023 Na+ ions / 1 mol Na+ ions) =
1.50*1018 Na+ ions present.
A NaCl crystal has a mass of 0.15mg. how many moles of Na^+ are present in...
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