Question

Pure copper is produced by the reaction of copper(I) sulfide with oxygen gas as follows: Cu_2S(s) + O_2(g) rightarrow 2 Cu(s) + SO_2(g) What mass of copper(l) sulfide is required in order to prepare 0.640 kg of copper metal? 0.481 kg 0.801 kg 160 kg 0.640 kg 0.320 kg The reaction of 11.9 g of CHClj with excess chlorine produced 13.3 g of CCl_4, carbon tetrachloride: 2CHCI_3+ 2C1_2 rightarrow 2CCl_4+ 2HCl What is the percent yield? 100.% 43.2 % 86.5 % 112% 57.7% S(s) + O_2(g) rightarrow SO_2(g) Classify this reaction. synthesis or combination combustion oxidation-reduction both (a) and (b) are correct (a), (b) and (c) are correct Pb(NO_3)_2(aq) + 2HCl(aq) rightarrow PbCl_2(s) + 2HNO_3(aq) Classify this reaction. acid-base precipitation oxidation-reduction single displacement both (a) and (b) are correct

Answer 1

40)
mass of Cu = 0.640 kg = 640 g
molar mass of Cu = 63.546 g/mol
number of moles of Cu = mass/molar mass
= 640/63.546
= 10.07 mol

from reaction gives,
moles of Cu2S required = moles of Cu/2
= 10.07/2
= 5.035 mol

molar mass of Cu2S = 159.16 g/mol

mass of Cu2S = number of moles * molar mass
= 5.035 * 159.16
= 801 g
= 0.801 kg
Answer: b

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