In 1928, 1.0 g of rhenium. Re, was isolated from 660 kg of the ore molybenite. T
ID: 498362 • Letter: I
Question
In 1928, 1.0 g of rhenium. Re, was isolated from 660 kg of the ore molybenite. The percent mass of this element in the molybenite was a) 0.66%. b) 0.15%. c) 6.6 times 10^3%. d) 3.5 times 10^-4% e) 1.5 times 10%. What is the percentage by mass of sulfur in copper(l) sulfide, CU_2S? a) 20.1% b) 28.4% c) 38.4% d) 46.7% e) 59.4% What is the percentage by mass of chlorine in DDT, C_14H_9Cl_5? a) 27.4% b) 36.4% c) -63.4% d) 50.0% e) 71.0% How many grams of hydrogen atoms are present in 18.6 g of water?Explanation / Answer
53). Mass of Re in ore = 1.0 g = 0.001 kg
Mass of ore = 660 kg
Percent by mass of Re in ore = ( 0.001 / 660 ) * 100
= 1.5 x 10-4 %
54). Atomis mass of copper = 63.54 g/mol
Molar mass of Cu2S = 159.16 g/mol
Mass of Cu is 1 mole Cu2S = 2 * 63.54
= 127.08 g/mol
Percent by mass of Cu in Cu2S = ( 127.08 / 159.16 ) * 100
= 79.84 %
55). Atomic mass of chlorine = 35.45 g/mol
Molar mass of DDT = 354.49 g/mol
Mass of Cl is 1 mole DDT = 5 * 35.45
= 177.25 g/mol
Percent by mass of Cu in Cu2S = ( 177.25 / 354.49 ) * 100
= 50.00 %