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#16 Find the mass in grams of 4.52 x 10 -3 moles of C 20 H 42 4.52 x 10 -3 moles 1 grams= Mult. by Molar Mass 282.0 g 1mole X 1.27

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#17 Calculate the mass in grams of 2.5 moles of Iron (II) hydroxide 2.5 moles 1 grams= Mult. by Molar Mass 89.8.0 g 1mole X 1.27 Fe(OH) 2

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#18 Find the number of moles in 3.70 x 10 -1 (.370) grams of boron 3.70 x 10 -1 grams 1 moles= divide by Molar Mass 1 mole B 10.8 g X.0343 B 10.8

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#19 Calculate the number of moles in 75.0 g of dinitrogen trioxide 75 g 1 moles= divide by Molar Mass 1 mole 76.0 g X.99 N 2 O 3 = 76.0g/mole

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20. What is the volume of these gases at standard temperature and pressure? (STP) for most gases: 22.4 Liters 1 mole a. 3.20 x 10 -3 moles CO 2 b. 3.70 moles N 2 mult. by 22.4 3.20 x 10 -3 mol 1 x 22.4 liters 1 mole =.0717 liters 3.7 mole N 2 1 x 22.4 liters 1 mole = 82.9 liters N 2

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21. At STP (standard temp. and pressure), what volume do these gases occupy? for most gases: 22.4 Liters 1 mole a. 1.25 moles He b..335 moles C 2 H 6 mult. by 22.4 1.25 mol 1 x 22.4 liters 1 mole = 28.0 liters He.335 mole C 2 H 6 1 x 22.4 liters 1 mole = 7.5 liters C 2 H 6

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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? 3.58 g 1 liter ? g 1 mole 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: x 22.4 liters 1 mole = 80.2

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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 1 mole x 22.4 liters ? g 1liter = 3.74

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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

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25. What is the volume of one mole of any gas at STP? 22.4 Liters 1 mole

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26. How many grams are in 5.66 moles of CaCO 3 ? 5.66 moles x 100.1 g = 567 g CaCO 3 1 1 mole

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27. Find the number of moles in 508 g of ethanol (C 2 H 6 O)? C 2 H 6 O = 46.0g/mole 508 grams x 1 mole = 11.0 moles 1 46.0 g

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28. Calculate the volume, in liters, of 1.50 mol of Cl 2 at STP. 1.5 moles x 22.4 liters = 33.6 moles 1 1 mole

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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 x 22.4 liters = 39.9 g 1liter 1 mole 1 mole

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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. NH 3 = 17.0g/mole Cl 2 = 71.0g/mole SO 2 = 64.1g/mole N 2 = 28.0g/mole CH 4 = 16.0g/mole 1.25 g x 22.4 liter = 1 liter 1 mole 28g mole

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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. NH 3 = 17.0g/mole Cl 2 = 71.0g/mole SO 2 = 64.1g/mole N 2 = 28.0g/mole CH 4 = 16.0g/mole 2.86 g x 22.4 liter = 1 liter 1 mole 64.1g mole

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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. NH 3 = 17.0g/mole Cl 2 = 71.0g/mole SO 2 = 64.1g/mole N 2 = 28.0g/mole CH 4 = 16.0g/mole 0.7134 g x 22.4 liter = 1 liter 1 mole 16.0g mole

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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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