#16 Find the mass in grams of 4.52 x 10-3 moles of C20H42 Mult. by Molar Mass 4.52 x 10-3 moles 1 X 282.0 g 1mole = 1.27 grams #17 Calculate the mass in grams of 2.5 moles of Iron (II) hydroxide Fe(OH) Mult. by Molar Mass 2.5 moles 1 X 89.8.0 g 1mole = 225 2 grams #18 Find the number of moles in 3.70 x 10-1 (.370) grams of boron B 10.8 divide by Molar Mass 3.70 x 10-1 grams 1 X 1 mole B = 10.8 g .0343 moles #19 Calculate the number of moles in 75.0 g of dinitrogen trioxide N2O3 = 76.0g/mole divide by Molar Mass 75 g 1 X 1 mole 76.0 g = .99 moles 20. What is the volume of these gases at standard temperature and pressure? (STP) mult. by 22.4 a. 3.20 x 10-3 moles CO2 3.20 x 10-3mol 1 22.4 liters 1 mole x b. 3.70 moles N2 3.7 mole N2 1 x 22.4 liters 1 mole =.0717 liters for most gases: 22.4 Liters 1 mole 82.9 liters N 2 = 21. At STP (standard temp. and pressure), what volume do these gases occupy? mult. by 22.4 a. 1.25 moles He 1.25 mol 1 22.4 liters 1 mole x b. .335 moles C2H6 .335 mole C2H6 1 x 22.4 liters 1 mole for most gases: 22.4 Liters 1 mole =28.0 liters He 7.5 liters C H 2 6 = 22. A gaseous compound composed of sulfur and oxygen, which is linked to the formation of acid rain, has a density of 3.58 g/liter at STP. What is the molar mass of this gas? We are given the gas in units of g/liter and need to find the molar mass which is in units of g/mole. Therefore we need to use the relationship between liters and moles (22.4 liters/mole) to solve this: 3.58 g 1 liter x 22.4 liters = 1 mole 80.2? g 1 mole 23. What is the density of krypton gas at STP? Krypton has like all normal gases 22.4 liters/mole at STP. Therefore, knowing this and the molar mass of krypton (from the periodic table) we solve as follows? 83.8 g Kr x 1 mole 1 mole = 22.4 liters 3.74? g 1liter 24. Describe how to convert between the mass and the number of moles of a substance divide. by Molar Mass multiply by Molar Mass To go from grams to moles you need to divide by the molar mass To go from moles to grams you need to multiply by the molar mass 25. What is the volume of one mole of any gas at STP? 22.4 Liters 1 mole 26. How many grams are in 5.66 moles of CaCO3? 5.66 moles x 100.1 g 1 1 mole = 567 g CaCO3 27. Find the number of moles in 508 g of ethanol (C2H6O)? C2H6O = 46.0g/mole 508 grams x 1 1 mole 46.0 g = 11.0 moles 28. Calculate the volume, in liters, of 1.50 mol of Cl2 at STP. 1.5 moles 1 x 22.4 liters 1 mole = 33.6 liters 29. The density of an elemental gas is 1.7824 g/liter at STP. What is the molar mass of the element? 1.7824 g 1liter x 22.4 liters 1 mole = 39.9 g 1 mole 30. The densities of gases A,B,and C are 1.25 2.86 and 0.7134 respectively. Calculate the molar mass of each substance. Identify each substance as ammonia, sulfur dioxide, chlorine, nitrogen, or methane. SO2 1.25 g x 22.4 liter = 1 liter 1 mole = 64.1g/mole 28g mole Cl2 = 71.0g/mole NH3 = 17.0g/mole N2 = 28.0g/mole CH4 = 16.0g/mole 30. The densities of gases A,B,and C are 1.25 2.86 and 0.7134 respectively. Calculate the molar mass of each substance. Identify each substance as ammonia, sulfur dioxide, chlorine, nitrogen, or methane. SO2 2.86 g x 22.4 liter = 1 liter 1 mole 64.1g mole = 64.1g/mole Cl2 = 71.0g/mole NH3 = 17.0g/mole N2 = 28.0g/mole CH4 = 16.0g/mole 30. The densities of gases A,B,and C are 1.25 2.86 and 0.7134 respectively. Calculate the molar mass of each substance. Identify each substance as ammonia, sulfur dioxide, chlorine, nitrogen, or methane. 0.7134 g x 22.4 liter = 1 liter 1 mole 16.0g mole NH3 SO2 = 17.0g/mole Cl2 N2 = 64.1g/mole = 71.0g/mole = 28.0g/mole CH4 = 16.0g/mole 31. Three balloons filled with three different gaseous compounds each have a volume of 22.4 L at STP. Would these balloons have the same mass or contain the same number of molecules? Explain They would have the same number of molecules because the rule states that equal volumes of gases contain equal numbers of molecules. The masses are probably different depending on the molar mass of each gas.

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