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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: kandyfloss on November 29, 2009, 02:26:20 PM

Title: Stoichiometry question {Urgent}
Post by: kandyfloss on November 29, 2009, 02:26:20 PM

Ok here is another question i'm stuck up with.I'm using the {Urgent} tag because i've a test tomorrow. :-[

The red color of blood is due to haemoglobin.It contains 0.335% by mass of Fe. 4 atoms of Fe are present in each molecule of haemoglobin.If the atomic mass of Fe=55.84 g/mol estimate the molar mass of haemoglobin.

Title: Re: Stoichiometry question {Urgent}
Post by: pear on November 30, 2009, 12:08:20 AM

When doing stoichiometric conversions, think "what do I need?"  Since the end-point needs to be "grams hemoglobin/mol," I'm going to invert the ".335g Fe/100g hem." the word-problem presents to have grams of hemoglobin in the numerator.  Then plug in what you have (keeping in mind that the numerator/denominator should cancel one of the preceding denominators/numerators).  And remember a mol has 6.022 x 10²³ molecules!


100g hem.      55.84g Fe                      1 mol Fe                        4 molecules Fe      6.022 x 10²³ molecules hem.
   .335g Fe         mol Fe           6.022 x 10²³ molecules Fe         1 molecule hem.                1 mol hem.


Good luck on the exam!