Chem Empirical Molecular Formula Molarity Dilution Review Key

Name Molarity problems Hour 1. 1L mL 2. Calculate the molarity of the following solutions a. 1.5 g of NaCl is dissolved in water to make 250 mL of solution Sg 58.449 = 1026 mol M=026 mol =1.104M 25L b. 0.4 g of NaOH is dissolved in water to make 150 mL of solution 4g/Imol 40 =.01 mol M= 01 mol ISL 1.067M 1 3. How many moles of AICI, are in 100 mL of a 0.50M solution? 0.5M mol mol.05 mol AlCl3 4. How many moles of Ca(OH), are in 25 mL of 1.5M solution? losm= mol 025 L mol=1.038mol Ca(OH) 5. A reaction calls for the use of 5.00 mol of NH₂OH. You have a bottle of 1.5M NH4OH. How many milliters of the solution should you add? 1.sm: smol X X= 3.333 L = 3333mL 6. A reaction calls for the use of 0.33 mol H₂SO₄. You have a bottle of 0.1M H₂SO₄. How many mL should you add? Im= 33 mol X = 3.3 L 3300 mL 7. How many moles KCIO3 are in 30 mL of a 0.100 M solution? How many grams? I m = mol .03L mol = 1003 mol KC103 or 122.5sg = Imol 1368g 8. A lab procedure calls for the use of 100 mL of 0.5M KOH. How many grams of KOH should you add to water to make this solution? .5m= mol IL 05 mol KOH 56.11 Imol 9 12.819 KOH 9. A lab procedure calls for 40 mL of 0.1 M NaHCO₃. You have a stock bottle of 2.0 M NaHCO₃. How many milliliters of the stock solution should you use to make the required solution? How many milliliters of water? (0.1 M)(0.04 L) = (2.0 M)V₂ V₂ = 0.002 L = 2 mL of solution 40 mL - 2 mL = 38 mL of water 10. A lab procedure calls for 50 mL of 0.02 M Li₂SO₄. You have a stock bottle of 1.0 M Li₂SO₄. How many milliliters of the stock solution should you use to make the required solution? How many milliliters of water? (0.02 M)(0.05 L) = (1.0 M)V₂ V₂ = 0.001 L = 1 mL of solution 50 mL - 1 mL = 49 mL of water 11. A lab procedure calls for 50 mL of 0.25 M NaOH. You place 100 g of NaOH in enough water to make 1.00 L of solution. How many mL of this solution should you use to make the solution called for in the lab procedure? 100 g NaOH / (40 g/mol) = 2.5 mol NaOH M = 2.5 mol / 1 L = 2.5 M (0.25 M)(0.05 L) = (2.5 M)V₂ V₂ = 0.005 L = 5 mL of solution 12. What information is conveyed by the following label: 0.5 M NaOH? 0.5 moles of NaOH per every 1 L of solution 13. If you evaporate 32 mL of a 0.50 M CuSO₄ solution to dryness, how many grams of solid copper sulfate would be left on the bottom of the beaker? 0.5 M = 0.5 mol/L 0.032 L * 0.5 mol/L = 0.016 mol CuSO₄ 0.016 mol CuSO₄ * (159.62 g/mol) = 2.55 g CuSO₄ 14. What is the molarity of a solution made by dissolving 11.7 g of NaCl in 250 mL of water? 11.7 g NaCl / (58.44 g/mol) = 0.2 mol NaCl M = 0.2 mol / 0.25 L = 0.8 M NaCl 15. How many mL of a 0.5 M K₂Cr₂O₇ must be evaporated to dryness in order to end up with 2.948 g of solid K₂Cr₂O₇? 2.948 g K₂Cr₂O₇ / (294.18 g/mol) = 0.01 mol K₂Cr₂O₇ (0.5 M)(V₂) = 0.01 mol V₂ = 0.02 L = 20 mL 16. Starting with solid copper (II) sulfate, how would you prepare 100 mL of a 0.25 M CuSO₄ solution? Give details. Dissolve 3.99 g CuSO₄ in water Fill water to 100 mL line Shake 17. An ace chemistry student mixes 60 mL of a 0.5 M NaOH solution with 140 mL of a 0.3 M NaOH solution. What is the molarity of the resulting sodium hydroxide solution? 0.06 L * 0.5 M = 0.03 mol NaOH 0.14 L * 0.3 M = 0.042 mol NaOH Total moles = 0.03 + 0.042 = 0.072 mol New volume = 0.06 L + 0.14 L = 0.2 L Molarity = 0.072 mol / 0.2 L = 0.36 M Image Analysis Text Content: Empirical/Molecular Formula and Molarity/Dilution Review 1. Explain the process of an ionically bonded salt dissolving. The water molecules pull apart the compounds into their ions. 2. What are three ways to help a solute dissolve in a solvent? Increase temperature Agitate solution Add more solvent 3. Write the empirical formula of C₂H₂O and N₂O. CH₂ NO₃ 4. A molecule with an empirical formula of CO has a molecular mass of 84 g/mol. What is its molecular formula? 12 + 16 = 28 84 / 28 = 3 C₃O₃ 5. A compound was analyzed and found to contain 13.5 g Ca, 10.8 g O, and 0.675 g H. What is the empirical formula of the compound?   13.5 g Ca / 40.08 g/mol = 0.337 mol Ca 10.8 g O / 16.00 g/mol = 0.675 mol O 0.675 g H / 1.01 g/mol = 0.675 mol H Divide by the smallest number of moles: 0.337 mol Ca₁O₂H₂ = Ca(OH)₂ 6. NutraSweet is 57.14% C, 6.16% H, 9.52% N, and 27.18% O. Calculate the empirical formula of NutraSweet and find the molecular formula. (The molar mass of NutraSweet is 294.30 g/mol).   57.14 g C / 12.01 g/mol = 4.76 mol C 6.16 g H / 1.01 g/mol = 6.10 mol H 9.52 g N / 14.01 g/mol = 0.68 mol N 27.18 g O / 16.00 g/mol = 1.70 mol O Divide by the smallest number of moles: 0.68 mol C₇H₉N₁O₂ Molecular formula: (C₇H₉N₁O₂) * (294.30 g/mol / 146.17 g/mol) = C₁₄H₁₈N₂O₄ 7. A 3.927 g sample of glycerin was found to contain 1.536 g carbon, 0.345 g hydrogen, and the rest oxygen. Find the empirical formula of this important lubricant. 1.536 g C / 12.01 g/mol = 0.128 mol C 0.345 g H / 1.01 g/mol = 0.342 mol H 3.927 g - 1.536 g - 0.345 g = 2.046 g O 2.046 g O / 16.00 g/mol = 0.128 mol O Divide by the smallest number of moles: 0.128 mol C₁H₂O₁ = CH₂O 8. A 4 g sugar cube (sucrose: C₁₂H₂₂O₁₁) is dissolved in a 350 mL teacup filled with hot water. What is the molarity of the sugar solution? 4 g / 342.34 g/mol = 0.012 mol 0.012 mol / 0.350 L = 0.033 M 9. A 250 ml solution is made with 0.50 moles of NaCl. What is the molarity of the solution? M2M NaCl 25 10. What is the volume of 3.0 M solution of NaCl made with 526g of solute? 52 leg Nall Imol 158.449 Naci = 9 mol 3.0M 9 mol X X= 3L 11. How many grams of CaCl, would be required to produce a 3.5 M (molar) solution with a volume of 2.0 L? 7mol Callz 110.989 Callz 2 776-8log 3.sm 2L X = 7 ml Imol 12. How many moles of Sr(NO3)2 would be used in the preparation of 2.50 L of a 3.5 M solution? 3.SM: 2.5L 3.5m X X=8.75 moll 13. Calculate the amount of 1 M NaOH aqueous solution needed to make 100 mL of 0.5 M NaOH aqueous solution. Mi Vi=MzVz (1)V=SM・L) V=OSL =150ML 14. What would be the concentration of a solution made by diluting 45.0 mL of 4.2 M KOH to 250 mL? M.Vi=MzVz (4.2m) (.04SL)= M2(.25L) M2.756 M 15. If I have 340 mL of a 0.5 M NaBr solution, what will the concentration be if I add 560 mL more water to it? MiVi = M2V2 (SM) (.340L)=Mz(.9L) total volume: 900 mL TM2=.189M 16. If I dilute 250 mL of 0.10 M lithium acetate solution to a volume of 750 ml, what will the concentration of this solution be? (.1m) (250) M2 (.750) Im TM2,033 M