7. hat is the molar mass of a gas a. 16.0 g/mol that has a density of2.e2 Lat 20

Question

7. hat is the molar mass of a gas a. 16.0 g/mol that has a density of2.e2 Lat 200 atm and 25.o c? d. 32.0 g/mol b. 28.0 g/mol c. 2.69 g/mol e. 64.0 g/mol 8. Metallic copper can be obtained from the mineral chalcocite cu so. What is the mass percent of copper in chalcocite? a. 33.54% b. 66.46% d. 79.85% e, 20.15% c. 57.47% 9. Enriched weapons uranium consists of 80% uranium.235 235.044 amu) and 20% (238.051 amu). at is the average atomic mass of weapons-grade uranium, assuming the percentages are exact? a. 238.051 amu d. 236.547 a b. 235.754 amu e. 235.645 amu c. 235.044 amu

Explanation / Answer

7)

d= PM/RT

therefore; M= dRT/P = 2.62 × 0.0821 × 298.15/2 = 32.066 g/mol

8)

Formula for Chalcocite is Cu2S

Therefore Molar mass of Cu2s = (63.6 × 2) +32.07= 159.27

Now percent of copper = [(63.6 × 2)/159.27]×100 = 79.86%

9)

the average atomic mass is the weighted sum of the atomic masses

uranium-235 is 80% = 235*80/100= 188

uranium-238 is 20% = 238*20/100= 47.6

Average atomic mass of uranium = 188+47.6= 235.6 amu

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