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Mole Review 1. Find the molar mass of the following compounds: A) K3Fe(CN)6 B) C12H22O11 329.2 g/mol 342.0 g/mol C) C2H5OH 46.0 g/mol 2. What is the mass of 1.0 mole of the following compounds? A) Ca(NO3)2 B) CI4 C) NaHSO4 164.1 g/mol 519.6 g/mol 120.1 g/mol A) Na2CO3 E) CH4 B) Cl2 F) OF2 C) Ag G) O3 D) NaCl H) KHSO4 3. Identify boxes that are elemental _______B, C, and G________ 4. Identify boxes that composed of atoms ________C___________ 5. Identify boxes that contain molecules __B, E, F, and G____ 6. Identify boxes that contain formula units ____A, D, and H______ 7. Identify boxes that contain polyatomic ions __A, and H ____ 8. Identify boxes that represent molecular compounds __E and F____ 9. Identify boxes that represent molecular elements ___B and G____ 10. The density of oxygen gas at STP is 1.43 g/L and the density of chlorine gas is 3.17 g/L at STP. A. What can be inferred about the number of particles if both oxygen and chlorine are kept in 1.0 Liter containers at STP? Explain. Since both have the same volume at the same Temp and Pressure, they have equal number of particles. This is according to Avogadro’s hypothesis: EQUAL VOLUMES OF GASES AT THE SAME TEMP AND PRESSURE HAVE EQUAL NUMBER OF PARTICLES. B. How much more massive is a molecule of chlorine compared to a molecule of oxygen. 3.17 g/L 1.43 g/L = 2.22. Chlorine is 2.22 time more massive than oxygen. C. What is the atomic mass of chlorine if oxygen’s atomic mass is 16.0 grams? Since both chlorine and oxygen molecules are diatomic the ratio of Cl to O atoms is also 2.22. Consequently the atomic mass of Cl is 2.22 times more massive than O or 2.22 x 16.0 = 35.5 11. Sodium chloride is determined to be composed of 39.3 % Na and 60.7% Cl. A. How much more or less massive is Na compared to Cl? Since NaCl has one atom of each element then the Cl mass is 60.7 39.3 or divided out the mass of Cl is 1.54 times more massive than Na. Stated differently a Na atom has mass that is just a fraction that of a Cl atom. An atom of sodium is 0.647 as massive as that of a Cl atom. B. What is the mass of Na relative to Cl? (35.5)•(0.647) = mass of Na = 23.0 To the nearest tenth. 12. Suppose it is learned that Na is 1.92 times more massive than carbon. A) What is the atomic mass of carbon to the nearest 0.l gram? Na C = 1.92 rewritten C = Na 1.92 = 23.0 1.92 = 12.0 mass of C B) A compound of carbon and chlorine is formed and C makes up 7.79 % of the total mass and 92.2% is chlorine. How much more massive is chlorine in this compound than carbon? Based on preceding questions Cl is 35.5 and C is 12.00 which implies that Cl is (Cl C) is 2.96 more massive than C. Data from part B indicated Cl is not in a 1:1 ratio with C since ClC =92.2 7.79 = 11.88 which is much more than the expected 2.96 if the Cl:C ratio were 1:1. Note that 11.882.96 = 4.01. This implies there are four times as many Cl atoms than there are C atoms. C. What is the formula of this compound? CCl4 This can be confirmed by determining the empirical formula from the data in part B. 13. Hydrogen peroxide decomposes into 9.00 grams of water and 5.6 L of oxygen at STP. How many moles of water and moles of oxygen were formed? 1mol mols H 2O 9.00gH 2O x 0.500mols 18.0g mols O2 5.6L O2 x 1mol 0.25mols 22.4L 14. Potassium chlorate decomposes into 0.200 moles of KCl and 0.300 moles of O2. How many grams of KCl were formed and how many liters of oxygen at STP? 74.6g 14.9grams mol 22.4L L of O2 0.300mol x 6.72L mol gKCl 0.200mol x 15. Calcium hydroxide decomposes to produce 5.60 grams of CaO and 6.02 x 1022 molecules of H2O. How many formula units of CaO are produced and how many grams of H2O are produced? 1mol 6.02x10 23 units units of Ca O 5.60g x x 6.01x10 22 units 56.1g 1mol gramsH2O 6.02x10 22 molecules x 16. Calcium carbonate decomposes into 8.80 grams of CO2 and 0.200 moles of CaO. How many liters of CO2 are produced at STP, and how grams of CaO are produced simultaneously? L of CO2 8.80grams x g of CaO 0.200mol x 1mol 18.0g x 1.80grams 6.02x10 23 molecules 1mol 1mol 22.4L x 4.48L 44.0g 1mol 56.1g 11.2g 1mol For questions 17-20: In the equation CaO + SO3 CaSO4, 11.24 grams of CaO reacts with an unknown amount of SO3 to produced 27.24 grams of CaSO4. 17. How many grams of SO3 were utilized in the reaction? 11.24 g + ? (SO3) = 27.24 X or SO3 = 16.00 grams 18. Which law concerning the composition of matter is used to answer the previous question? Answer: Law of Conservation of Matter. 19. How many liters of SO3 were used in the reaction? 1mole 22.4L L of SO3 16.00g x x 4.47L You may also have 4.48L. 80.1g 1mole 20. How many moles of SO3 were used in the reaction? 1mole L of SO3 16.00g x 0.200mol 80.1g 21-23. What is the % H and % O in H2O and in H2O2? For H2O = 2.0/18.0 x 100 = 11.1% or 11% For H2O2 = 2.0/34.0 x 100 = 5.88 or 5.9% 22. How many grams of oxygen are present if there is 1.00 grams of O in both H2O and H2O2? For H2O = 16.0/18.0 x 1.00 = 0.888 grams For H2O2 = 32.0/34.0 x 1.00 = 0.941 grams SKIP PROBLEMS 23-25 *********************************************************************** 26. Avogadro’s hypothesis is sometimes rendered as Avogadro’s Law expressed as V1 V2 n1 n1 If 24.45 L of gas contains 1.00 mole of gas at 25°C and 1 atmosphere pressure, then how many moles will be in 36.0 L at the same temperature and pressure. 24.45L 36.0L 1.00mole x mole 27. To find the density of a gas at STP simply divide the molar mass by the molar volume (22.4 L). What is the density of He gas? MM 4.00g /mol Density 0.179g /mol MV 22.4L /mol SKIP THESE PROBLEMS 28-30 *********************************************************************** 31. How many moles of water are needed to fill a 5.00-gallon aquarium? One gallon is equal to 3.75L. The density of water is 1.0 g/mL. mols of H 2O 5gal x 3.75L 1000mL 1g 1mol x x x 1000mol 1 gal 1L 1mL 18.0g