SOLUTIONS and DILUTIONS
Name:_______________________ BIOL 1406__________________ Date______________ SOLUTIONS and DILUTIONS Part 1. Look up information Define the following terms: Solution Solvent Solute What is Avogadro’s number? When diluting an acid, how should the water and acid be combined? Part 2 SDS and Safety Read the SDS (Safety Data Sheet) for HCl at the website https://www.flinnsci.com/sds/ What personal protection equipment should be used when working with hydrochloric acid (HCl)? What first aid should be used if HCl is spilled on the skin? What should be done if HCl gets into your eyes? Introduction: A solution is a liquid that is a homogeneous mixture of two or more substances. The solvent is the dissolving agent of a solution. Water will be the solvent most commonly used during lab this semester. The solute is the substance that is dissolved in a solution. Part 2. Dilutions 1 Name:_______________________ BIOL 1406__________________ Date______________ To do a dilution, you would normally use test tubes. Special precautions would be taken if dealing with acids or bases. HCl is HydroChloric Acid and would burn your hands. You know it is an acid because it has a H in front of the formula. Bases have an OH at the end of the formula and a salt has neither, such as NaCl – Sodium Chloride/table salt. To prepare a series of two 10% dilutions of 1M HCl: 1. Wear goggles and lab coat and nitrile gloves. 2. Label three test tubes or other suitable containers 1, 2, and 3. 3. Fill test tube 1 with 10 mL of 1M HCl 4. Use the formula to determine how much water should be added to test tube #2 to prepare a 10% dilution. The final desired volume for this dilution is 10 mL. Remember add the water first! (have) (need) V i X Ci = Vf X Cf n X 1M HCl = 10 mL X 0.1M HCl n = 10 mL X 0.1 M 1M n = volume of 1M HCl used to make the new solution n = 1 mL of 1M HCl 10 mL (final volume) – 1 mL (volume of the 1M HCl) 9 mL (volume of water used for the dilution) This is how much water to add to test tubes 2 and 3 5. Fill test tube 2 with 9 mLs water and add 1 mL of the solution in test tube 1 to test tube 2. 6. Mix the HCl and water by rolling the test tube a little between your hands. An important safety rule must be followed when diluting acids: Always Add Acid to Water. This rule must be followed in order to prevent splattering of the acid, because the solution will heat up. 7. Repeat step 5 and 6 for test tube 3, pulling the 1 mL of solution from test tube 2 this time. Questions to answer: 1. Explain how the final dilution in test tube 3 should have been prepared, giving each step in detail. 2. Volume is always mL and C is Molar concentration. You need 3 numbers to be able to plug in the formula. Solve the following dilution problems and check your answers against the answer sheet. a. If I add 30 mL of water to 20 mL of a .10 M of NaOH solution, what will the molarity of the diluted solution be? _____________________ 2 Name:_______________________ BIOL 1406__________________ Date______________ b. If I add 25 mL of water to 10 mL of a .20 M of NaOH solution, what will the molarity of the diluted solution be?______________________ c. I have 1 liter of stock 2M HCl, but I’m on a tight budget and only need to use 50 mLs of a 1M solution of HCL. How can I prepare this 50mLs and keep my lab manager happy? d. I’m preparing 100 mLs of medication for a patient at the hospital. It must be diluted to 10% of the original strength or the patient will die when they receive their medication. In order to keep the patient alive and avoid a lawsuit, how should I prepare this medication? Part 3. Molar solutions We have already worked with molar solutions, but you also need to know how they are made. Molarity is a measurement of how concentrated the solution is in the number of particles present in the solution. One mole contains Avogadro’s number of representative particles, whether they be molecules, ionic formula units, or atoms. The atomic mass on the periodic table is the mass of one mole of atoms of its element. To make a molar solution: 1. Go to the periodic table and look up the atomic mass of each element in the material being dissolved to make the solution. 2. Multiply each mass by the number of atoms of that element that are in the material. Look at the subscripts of the molecular formula to find out how many of each element are present. 3. Add all the masses up, and you have the mass of one mole of this material. Example: Sucrose Formula: C12H22O11 Molecular Weight X # of atoms in formula = Daltons C: _____ X ___________ = _____ Daltons H: _____ X ___________ = _____ Daltons O: _____ X ___________ = _____ Daltons Total molecular weight of sucrose = _____ Daltons. Convert Daltons to grams when preparing a molar solution by simply changing the units (1 Dalton = 1 gram). 4. Now that you know how much a mole of this material weighs, calculate how much water to dissolve it in. If you are making a 1M (1 molar) solution, add one mole in grams to 1,000 ml (1 liter) of water. Don’t just pour in 1,000 mL in that volumetric flask and add the material or it will be over 1,000 mL and be too dilute. Instead, add about half the water (500 mLs) and then add the material to be dissolved, then swirl to dissolve completely and finally add water until it reaches the 1,000 mL mark. 5. You will also make other concentrations of solutions. If the concentration is to be less than a mole, reduce the mass of the substance accordingly. If the concentration is to be greater than 1M, increase the mass added or reduce the volume of water accordingly. Use this formula: Molarity = moles/liter. Example: Make a .5M solution of HCl 3 Name:_______________________ BIOL 1406__________________ Date______________ H = 1.008 Daltons Cl = 35.45 Daltons Total = 36.46 Daltons = 36.46 grams .5M = X moles/1 liter .5M * 1 liter = X moles Number of moles = .5 .5 * 36.46 = 18.23 grams Add 500 mLs water to 1L volumetric flask, add the 18.23 grams HCl to the water, swirl to dissolve, then add water until it reaches the 1L or 1,000 mL mark. Answer the following questions: 1. How many mL should I use to make a 1M solution of MgBr2? 2. What is the mass of a mole of NH3? 3. How much CaCO3 should I use to make a 2M solution? 4. How much CaCO3 should I use to make a .25M solution? 5. What are the steps to make a 1M solution of NH3 – give the steps and the amounts of solute and solvent? Part 4. Percent Solutions You looked at molar solutions, which require the mass of one mole as calculated from the periodic table and the molecular formula and go into 1,000 mL, unless you need to make less than 1,000 mL – but you must keep the ratio of water to moles the same. Now look at percent solutions, which require much less calculation and are prepared in the same way, regardless of what the material is. No periodic table is needed for this kind of solution! To make a percent solution: 1. Change the percent into grams. 2. Measure out the grams. 3. Add about 50 mLs water to a 100 mL volumetric flask. 4. Add the grams of material to dissolve to the water in the flask and swirl to dissolve. 5. Fill the flask up to the 100 mL ring mark on the neck of the flask. Example: Make a 25% solution of HCL. Weigh out 25 grams of HCl, add to 50 mLs water in a 100 mL volumetric flask, swirl to dissolve, then fill with the 100 mL volumetric flask water until it reaches the 100 mL mark. Notice that a percent solution is grams out of 100 mLs. One hundred mLs of water will have a mass of 100g, so this is truly equal to a percent in grams. If you need to make less than 100 mLs, just reduce the grams by the same proportion. So if only 50 mLs is needed, you are halving the volume and thus you will also halve the mass: 12.5 grams in 50 mLs water (and it will require a 50 mL volumetric flask). 4 Name:_______________________ BIOL 1406__________________ Date______________ Answer the following questions. 1. What does percent mean? 2. How can a 5% solution be made – give the steps and the amounts of solute and solvent? 3. Why should you not add all the water first when making a solution? 5
Collepals.com Plagiarism Free Papers
Are you looking for custom essay writing service or even dissertation writing services? Just request for our write my paper service, and we'll match you with the best essay writer in your subject! With an exceptional team of professional academic experts in a wide range of subjects, we can guarantee you an unrivaled quality of custom-written papers.
Get ZERO PLAGIARISM, HUMAN WRITTEN ESSAYS
Why Hire Collepals.com writers to do your paper?
Quality- We are experienced and have access to ample research materials.
We write plagiarism Free Content
Confidential- We never share or sell your personal information to third parties.
Support-Chat with us today! We are always waiting to answer all your questions.
