90 g What is the molecular formula of the compound 10 points

# 90 g what is the molecular formula of the compound 10

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weighs 6.90 g. What is the molecular formula of the compound? (10 points) M(6.9*.0821*393.15)/.987=225.64 64.5% C=144, 13.5%H=30.46,21.6%O=48 C 12 H 30 O 3 9. What is the mass of the solid NH 4 Cl formed when 73.0 g of NH 3 ( g ) are mixed with an equal mass of gaseous HCl? What is the volume and identity of the gas remaining, measured at 14.0°C and 752 mmHg? (8 points) NH 3 ( g ) + HCl( g ) → NH 4 Cl (Reference: Chang 5.59) 1 mol NH 3 = 17.034g 73/17.034= 4.3 mols present 1 mol HCL = 36.458g 73/36.458=2.002 mols present 2 mol NH 3 + 2 mol HCL → 2 mol NH 4 Cl NH 4 Cl=107g 2
P V = n R T (.989)(V)=(2.3)(.0821)(287.15) V= 54.22/.989 V= 54.82 L NH 3 10. A mixture of gases contains 0.31 mol CH 4 , 0.25 mol C 2 H 6, and 0.29 mol C 3 H 8 . The total pressure is 1.50 atm. Calculate the partial pressures of the gases. (8 points) (Reference: Chang 5.67) P t =.29+.25+.31=.85 X 1 =.31/.85=.36 CH 4 X 2 =.25/.85=.29 C 2 H 6 X 3 =.29/.85=.34 C 3 H 8 CH 4 =.36*1.5= .54 atm C 2 H 6 =.29*1.5=.44 atm C 3 H 8 =.34*1.5=.51 atm 11. Propane (C 3 H 8 ) burns in oxygen to produce carbon dioxide gas and water vapor. (a) Write a balanced equation for this reaction. (b) Calculate the number of liters of carbon dioxide measured at STP (0c/1atm)that could be produced from 7.45 g of propane. (10 points) a) C 3 H 8 ( g ) + 5 O 2 ( g ) → 3CO 2 (g) + 4H 2 O b) 11.44l (Reference: Chang 5.109) 12. A 10.0 g piece of pure aluminum is placed in 75.0 mL of 0.54 M hydrochloric acid at STP condition. They react as follows: 2Al + 6HCl 3H 2 ( g ) + 2AlCl 3 Calculate the following: a. Volume, in liters, of hydrogen gas. (5 points) V=.0006*.0821*273.15= .13L H 2 b. Molarity of Al +3 . (Assume 75.0 mL solution.) (5 points) .0135 mols Al/.075 L = .18 M Al +3 c. Molarity of Cl . (Assume 75.0 mL solution.) (5 points) .039 mols Cl /.075 L = .52 M Cl 3

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