Finding the Molar Mass and Dealing with Moles (Answers to Exercises)

1 Finding the molar mass: 1) H2O 2) HgO 3) Hg2O 4) I2 5) I6) CH3OH 7) Ca(NO3)2 8) Al(OH)3 9) C12H22O11 10) Ba3(PO4)2 11) Sr(MnO4)2 12) (NH4)2Cr2O7 13) PtCl2(NH3)2 14) C23H40N7O17P3S 18.02 g mol 216.59 g mol 417.18 g mol 253.80 g mol 126.90 g mol 32.05 g mol 164.10 g mol 78.01 g mol 342.32 g mol 601.93 g mol 325.50 g mol 252.10 g mol 300.06 g mol 811.68 g mol water mercury (II) oxide mercury (I) oxide iodine iodide (methanol) calcium nitrate aluminum hydroxide (sucrose) barium phosphate strontium permanganate ammonium dichromate (cisplatin) (acetyl coenzyme A) Dealing with moles: 1) How many moles are there in 1 mol of moles? 6.022 × 1023 moles 1 mol mole × = 6 × 1023 moles 1 mol mole 2) How many atoms are there in 7.42 moles of tin? 6.022 × 1023 atoms Sn 7.42 mol Sn × = 4.47 × 1024 atoms Sn 1 mol Sn How many molecules are there in 3.14 moles of water? 3) 6.022 × 1023 molecules H 2O 3.14 mol H 2O × = 1.89 × 1024 molecules H 2O 1 mol H 2O How many ATOMS are there in 8.22 moles of H2 molecules? 4) 2 mol H 6.022 × 1023 atom H 8.22 mol H 2 × × × = 9.90 × 1024 atom H 1 mol H 2 1 mol H How many moles are there in 5.87x1024 molecules of NaCl 5) 1 mol NaCl 5.89 × 1024 molecules NaCl × = 9.78 m ol NaCl 6.022 × 1023 molecules NaCl How many moles are there in 9.46x1018 molecules of AgNO3? 6) 1 mol AgNO 3 9.46 × 1018 molecules AgNO 3 × = 1.57 × 10−5 m ol AgNO 3 6.022 × 1023 molecules AgNO 3 NEXT SECTION 1) 2) If a 1 liter flask contains 55.4 moles of H2O, how many atoms of hydrogen are in the flask? 2 mol H 6.022 × 1023 atoms H 55.4 mol H 2O × × = 6.67 × 1025 atoms H 1 mol H 2O 1 m ol H OR 23 6.022 × 10 molecules H 2O 2 atoms H 55.4 mol H 2O × × = 6.67 × 1025 atoms H 1 mol H 2O 1 molecules H 2O A sample has 1.93x1020 atoms of Iron. How many moles of Fe2O3 would this make? 1 mol Fe 2O 3 1 mol Fe 1.93 × 1020 atoms Fe × × = 1.60 × 10−4 mol Fe 2O 3 23 6.022 × 10 atoms Fe 2 m ol Fe OR 2 1.93 × 1020 atoms Fe × 3) 1 molecule Fe2O 3 1 mol Fe 2O 3 × = 1.60 × 10−4 mol Fe 2O 3 2 atom s Fe 6.022 × 1023 molecule Fe 2O 3 How many atoms of carbon are there in 6.15x10-8 moles of (CH3CH2CO2)2C6H4 12 m ol C 6.022 × 1023 atoms C 6.15 × 10−8 mol (CH 3CH 2CO 2 )2 C6 H 4 × × = 4.44 × 1017 atoms H 1 mol (CH 3CH 2CO 2 )2 C6 H 4 1 mol C OR 6.15 ×10−8 mol (CH3CH2CO2 )2 C6 H4 × 4) 5) 6.022 ×1023 molecules (CH3CH2CO2 )2 C6H4 12 atoms C × = 4.44 ×1017 atoms H 1 mol (CH3CH2CO2 )2 C6H4 1 molecules (CH3CH2CO2 )2 C6 H4 How many moles of Ra(CN)2 are present if you have 8.34x1027 atoms of N 1 mol Ra(CN)2 1 mol N 8.34 × 1027 atoms N × × = 6920 mol Ra(CN)2 6.022 × 1023 atoms N 2 mol N OR 1 mol Ra(CN)2 molecule Ra(CN) 1 2 8.34 × 1027 atoms N × × = 6920 mol Ra(CN)2 2 atoms N 6.022 × 1023 molecule Ra(CN)2 How many atoms of hydrogen are there in 1.23x10-4 moles of Aspartame, C14H18N2O5 1.23 × 10−4 mol C14 H18 N 2O 5 × 6.022 × 1023 molecules C14 H18 N 2O 5 18 atoms H × = 1.33 × 1021 atoms H 1 mol C14 H18 N 2O 5 1 molecules C14 H18 N 2O 5 OR 18 mol H 6.022 × 1023 atoms H 1.23 × 10−4 mol C14 H18 N 2O 5 × = 1.33 × 1021 atoms H × 1 m ol C14 H18 N 2O5 1 mol H Calculate the mass of 4.97x1024 molecules of sulfur dioxide. (Here is a curveball for you, but think about it and see if you can figure it out!) 1 mol SO 2 64.07 g SO 2 4.97 × 1024 molecules SO 2 × × = 529 g SO 2 23 6.022 × 10 molecules SO 2 1 m ol SO 2 NEXT SECTION 6) Like the last section, most of these can be done one of two ways. For time and space reasons, I am only putting on way on here, but convince yourself that it can be done the other way too… 1) What mass of rubidium is in 2.39x1020 molecules of Rb2SO4? 1 mol Rb 2SO 4 2 mol Rb 85.47 g Rb 2.39 × 10 20 molecules Rb 2SO 4 × × × = 0.0678 g Rb 6.022 × 1023 molecules Rb 2SO 4 1 mol Rb 2SO 4 1 mol Rb 2) How many sodium atoms are there in 6.53kg of NaHCO3? 6.53 kg NaHCO 3 × 1× 103 g NaHCO 3 1 mol NaHCO 3 1 mol Na 6.022 × 1023 atom Na × × × = 4.68 × 1025 atom Na 1 kg NaHCO 3 84.01 g NaHCO 3 1 mol NaHCO 3 1 mol Na 3) What is the mass of iodine in 8.52x1020 molecules of CeI3? 1 mol CeI 3 3 mol I 126.90 g I 8.52 × 1020 molecules CeI 3 × × × = 0.539 g I 6.022 × 1023 molecules CeI 3 1 mol CeI 3 1 mol I 4) How many oxygen atoms are in 1.2x10-3 grams of testosterone, C19H28O2? 1.2 × 10−3 g C19 H 28 O 2 × 1 mol C19 H 28 O 2 2 mol O 6.022 × 1023 atom O = 5.0 × 1018 atom O × × 288.47 g C19 H 28 O 2 1 mol C19 H 28 O 2 1 mol O 5) What is the mass of a snowflake (think) containing 2.67x1019 atoms of hydrogen? 1 mol H 2 O 18.02 g H 2 O 1 m ol H × × = 3.99 × 10−4 g H 2 O 2.67 × 1019 atoms H × 23 6.022 × 10 atom s H 2 mol H 1 mol H 2 O 6) How many nitrogen atoms in 1.05x1021 molecules of caffeine, C8H10N4O2? 3 1.05 × 1021 molecules C8 H10 N 4O 2 × 1 mol C8 H10 N 4O 2 4 mol N 6.022 × 1023 atoms N × × = 4.20 × 1021 atoms N 23 6.022 × 10 molecules C8 H10 N 4O 2 1 mol C8 H10 N 4O 2 1 mol N OR 4 atoms N = 4.20 × 1021 atoms N 1.05 × 10 molecules C8 H10 N 4O 2 × 1 molecules C8 H10 N 4O 2 21 Notice that the atom-to-molecule ratio is EXACTLY the same as the mole-to-mole ratio. This is always true. 7) What is the mass of a Vitamin C tablet that has 5.13x1021 atoms of oxygen? The formula for Vitamin C is C6H8O6. 1 m ol C6 H 8 O 6 176.14 g C6 H 8 O 6 1 mol O 5.13 × 10 21 atoms O × × × = 0.250 g C6 H 8 O 6 23 6.022 × 10 atoms O 6 mol O 1 m ol C 6 H 8 O 6 8) A sample of calcium acetate contains 5.98x1023 atoms of oxygen. What mass of hydrogen does it contain? 1 mol Ca(C2 H 3 O 2 )2 1 mol O 6 mol H 1.01 g H 5.98 × 10 23 atoms O × × × × = 1.50 g H 23 6.022 × 10 atom s O 4 mol O 1 m ol Ca(C2 H 3 O 2 )2 1 mol H 9) Home many iodine atoms are there in 28.3mg of carbon tetraiodide? 1× 10−3 g CI 4 1 mol CI 4 4 m ol I 6.022 × 1023 atoms I 28.3 mg CI 4 × × × × = 1.31× 10 20 atoms I 1 m g CI 4 519.61 g CI 4 1 mol CI 4 1 mol I