Preparation of Solutions: Rainbow Lab Name:______Partner:______Date Performed:______Date Due:Friday, Dec 5, 2014 (1 mark,C) Introduction: What do the effectiveness of a medicine, the safety of a chemical reaction, and the cost of an industrial process have in common? They all depend on solutions that are made carefully with known concentrations. A solution with a precise known concentration is called a standard solution. There are two ways to prepare an aqueous solution with a known concentration. You can make a dissolve a measured mass of pure solute in a certain volume of solution, or you can dilute a standard solution. In this lab you will practice preparing solutions of specific concentrations following the proper procedure and using the appropriate equipment. To test the accuracy of your measurements you will attempt to layer your solutions according to their density. Purpose: ______(2 marks,C) Materials: goggles 5 small beakers granulated sugar apron retort stand saturated sugar solution large test tube (110 mL) test tube clamp food colouring glass stir rod 25 mL graduated cylinder
Table 1: Concentration and Volume for Solutions Prepared by Diluting a Saturated Sucrose Solution Concentration Volume of Final Final Volume Food of Saturated Saturated Concentration Solution of Solution colouring Sugar Solution Sugar Solution of Solution (mL) (mol/L) (mL) (mol/L) 1 drop blue 1 purple 24.50 25.00 2 drops red 2 blue 1 drop blue 18.00 25.00
3 green 1 drop green 15.00 25.00
Table 2: Concentration, Mass and Volume for Solutions Prepared from Solid Sucrose Final Mass of Final Volume Food Concentration Solution Granulated of Solution colouring of Solution Sucrose (g) (mL) (mol/L) 4 yellow 1 drop yellow 6.50 25.00 1 drop red 5 red 0.01 25.00 Procedure: __ 1.Place a check mark in the space provided as you complete each step of the lab __ 2.Put on your apron and safety goggles. DO NOT take them off until the end of the lab. __ 3.Use the test tube clamp to secure your test tube to the retort stand. __ 4.Prepare solutions 1,2,and 3 by diluting the standard sugar solution according to the recipe in Table 1. a. Measure the correct volume of stock solution into a 25 mL graduated cylinder. b. Add food colouring, and then add water until the bottom of the meniscus is on the 25 mL mark of the graduated cylinder. c. Stir, then transfer the solution to a small beaker and stir again. d. Carefully and slowly us a pipette to transfer your solution to the test tube as directed by your teacher – the slower you add the solutions to the test tube the less the layers will mix together. __ 5. Prepare solution 4 and 5 from the solid sucrose according to the recipe in Table 2. a. Measure the correct mass of sugar and add it to your 25 mL graduated cylinder. b. Add food colouring, add water until the bottom of the meniscus is on the 25 mL mark of the graduated cylinder. c. Stir well so that solid does not stick to the bottom, then transfer the solution to a small beaker and stir again. d. Use the pipette to SLOWLY add this layer. Keep the pipette low into the test tube so they do not mix.
__ 6.Show your rainbow to the teacher to be graded (4 marks, A)
__ 7.Label your test tube and put it in the fumehood for a few days. Divide the clean up fairly between yourself and your partner. Make sure all glassware that came into contact with a sucrose solution is thoroughly washed with hot water and soap. Put away all of the equipment and then return to your lab area and wipe the lab bench with a moistened paper towel.
Analysis Questions: 1. The standard solution was made so that it is perfectly saturated at 20oC.
a) Use the solubility curve to determine the amount of sugar dissolved in 1.00 L of water? (1 mark,I)
b) Find the concentration of the stock solution in mol/L. Show all work. (3 marks,I)
2. Find the final concentration of each solution. Show all work including units and complete the table. (6 marks,I) Calculations 1 blue
2 green
3 yellow
(4 marks,I)
Solutio Calculations n 4 orange
5 red
3. If you were making solution 2 from solid sugar instead of by dilution, how much solid table sugar would you need to use? Show all calculations and include all units. (4 marks,I)
4. What volume of stock solution would you need to make solution 5 by diluting? Show all calculations and include all units. (4 marks,I)
5. What is the concentration of solution 4 in units of ppm and ppb? (4 marks,I) 6. What equipment determined the number of significant digits you could use? Explain how you could get more significant digits. (3 marks,A)
7. Go to the internet. What is your favourite type of candy? Briefly explain how it is made, or describe some interesting chemistry facts about it. (3 marks,A)
8. How is a lollipop like glass? Explain! (2 marks,A)
Bonus: Bring in some candy to share! Revised Dec 2014 Tested Rm207 Fall 2013 by KW