Question

1. Chalcopyrite(CuFeS2) is an abundant copper mineral that can be converted to elemental copper. How much Cu is there in 1.00 kg CuFeS2?

2. Combustion analysis of an unknown compound indicated that it is 92.23% C and 7.82% H. The mass spectrum indicated the molar mass is 78g/mol. What is the molecular formula of this unknown compound?

3. Ascorbic acid also known as Vitamin C, is an organic compound containing C,H, and O. The combustion of a 28.1 g sample of ascorbic acid produces 42.1g CO2 and 11.5 g H2O. Determine the empirical and molecular formula of ascorbic acid. The molar mass is 176g/mol.

Answer 1

1 Molas mass of chalcopyrite (Cutes? J = 185.5gmot) Atomic mass of lu = 63.5 g mott in 185.5gm chalcopy site (cures) contains = 63.5gm of u : I gin cu ress will contain = 63.5 gm of u 185.5 : 1.00kg or 1000 gm cutesy will contain = 63.5 x 1000 gm of cu. 185.5 Amount of Cu = 342 32 gul © Subbose, if we consider total maan 100gm, then there is 923 gm of c 2 7.62 gm of H in the compound. Atomic mass of C= 12 gmot! in No. of moles of c= gm.wt - 923 = 7.691 mores Atomic wt. 01 m.wt. Atomic mass of H= 1 gmort No. of moles of H= gu Atomicuti Ratio of moles of C&H CH Moles 7.641 : 7.62 Moles 7.691 7.82 - 1:1 Moles 7.69 7.691 in Embrical formula = CH. Molas mans of CH= 12 +1 = 13 9mmor! It is given that the molar mars = 78 gmort le nx(CH) = 78

nx 18 = 78 n = 7 us. 137 Molecular formula - C6H6 I 3 Mans of ascorbic aud = R6.19m The combustion of ascorbic and produces 421gm CO2 & 11.5m H2O. Mass of CO2= 12 + 2x16= 44 gm mot 1 1.6. 44 gm coa contains 12 gm of c. :. 42.19m Cong will contains 19x421 - 4483 u. % of carbon in ascorbic and = 11.482 4100 28.1 16 28.1 - 40.86% similary Mas of H₂O = 18 gmmott El lie 18 gm H₂O contains - agm of H. u 11.5 gm Hao will contain: 3 x 115 of H 1:278 gm of : % of H in a sorbic aud : 1278 - 4.55% of H :: Rest percentage in th compound should be orggen 2. % of 0 100 - 40.66-4.55 - 54.59% In ockhorskine compound, there is 40.66 gm c, 4.55gm Hp 54.59 gm O. Moles of C= gmot - 40.66 = 3.41 moles Atomic wt 12 Moles of H= 4.55 = 4.55 moles

& moles of = 54.59 = 3.41 moles 16 Molar ratio : H :0 3.41 4.55:3411 dividing by smallest no. ( H: 0 1: 1.33: 1 in integer for 3:4:3 in Emprical formula C 3 H u O3 :: Emporical motor masi = 3x12 +481 +1613 = 88 gm mor? Given molar mass = 176 gmmort ANG Nxb b = 176 (9=31 i Molecular formula = ( 3 H₂O3) = C6 HqO6