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Chemistry Help!! Can somebody please help me!!The label on a box of baking soda (sodiym...

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london123 | Student, Undergraduate | (Level 2) eNoter

Posted May 9, 2010 at 11:43 AM via web

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Chemistry Help!! Can somebody please help me!!

The label on a box of baking soda (sodiym hydrogen carbonate, NaHCO3) claims that there are 137mg of soium per 0.500g of baking soda. Comment on validity of this claim.

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hnystrom | High School Teacher | (Level 1) Assistant Educator

Posted July 11, 2010 at 8:32 AM (Answer #1)

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What you need to figure out is:

the number of grams in a mole of NaHCO3

how many moles of NaHCO3 are in .500 grams

how many grams of Na are in that fraction of a mole

The number of grams in a mole of sodium bicarbonate is 23.00(Na) + 1.00 (H) + 12.00 (C) + 3 x16.00 (O) = 84.00 g

The number of moles in .5 grams is .5/84.00 = .0059 moles

Each mole of NaHCO3 contains 1 mole of Na, so .500 g have .0059 moles of sodium.  That means .0059 x 23.00 = .1357 grams or 135.7 mg.  This is close enough to quoted number to be the same within rounding.

 

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