1.- Calculate the molar mass of the following substances: a)Li 2 CO 3 , b) CS 2

Question

1.- Calculate the molar mass of the following substances: a)Li2CO3, b) CS2 c)CHCl3(chloroform) , c)C6H8O6 (vitamin C), e)KNO3 , f) Mg3N2 2.- The molar mass of caffeine is 194.19 g. Is the molecularformula of caffeine C4H5N2O orC8H10N4O2? 3.- HOw many grams of sulfur (S) are needed to reactcompletely with 246 g of mercury (Hg) to form HgS? 1.- Calculate the molar mass of the following substances: a)Li2CO3, b) CS2 c)CHCl3(chloroform) , c)C6H8O6 (vitamin C), e)KNO3 , f) Mg3N2 2.- The molar mass of caffeine is 194.19 g. Is the molecularformula of caffeine C4H5N2O orC8H10N4O2? 3.- HOw many grams of sulfur (S) are needed to reactcompletely with 246 g of mercury (Hg) to form HgS? 2.- The molar mass of caffeine is 194.19 g. Is the molecularformula of caffeine C4H5N2O orC8H10N4O2? 3.- HOw many grams of sulfur (S) are needed to reactcompletely with 246 g of mercury (Hg) to form HgS?

Explanation / Answer

(1 ) a) Li2CO3    molar mass : 2( 7 ) + 12 + 3 ( 16 ) = 74 g b) CS2 molar mass : 12 + 2 ( 32 ) = 76 g c) CHCl3(chloroform) molar mass : 12 + 1 + 3 ( 35.5 ) = 119.5 g c) C6H8O6 (vitaminC) molar mass : 6 ( 12 ) + 8 ( 1 ) + 6 ( 16 ) = 176 g e) KNO3 molar mass : 39 + 14 + 3 ( 16 ) = 101 g molar mass : 39 + 14 + 3 ( 16 ) = 101 g f) Mg3N2 molar mass : 3 ( 24 ) + 2 ( 14 ) = 100 g (2) C4H5N2O molar mass : 4( 12 ) + 5 ( 1 ) + 2 ( 14 ) + 16 = 97g C8H10N4O2 molar mass : 8 ( 12 ) + 10 ( 1 ) + 4 ( 14 ) + 2 ( 16 ) = 194g So, the molecular formula of caffeine isC8H10N4O2 ( 3 )                           S + Hg ----> HgS                        32.064 grams of Sulphur require to react completly with 200.59 g ofHg                                              xgrams of Sulphur require to react completly with 246 g ofHg x = ( 32.064 * 246 ) / 200.59      = 39.3227 g molar mass : 8 ( 12 ) + 10 ( 1 ) + 4 ( 14 ) + 2 ( 16 ) = 194g So, the molecular formula of caffeine isC8H10N4O2 ( 3 )                           S + Hg ----> HgS                        32.064 grams of Sulphur require to react completly with 200.59 g ofHg                                              xgrams of Sulphur require to react completly with 246 g ofHg x = ( 32.064 * 246 ) / 200.59      = 39.3227 g                       xgrams of Sulphur require to react completly with 246 g ofHg x = ( 32.064 * 246 ) / 200.59      = 39.3227 g

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