How to Dilute a Solution — Transcript

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1. 0:00[Music]
2. 0:10hi I'm Jared Heyman an assistant
3. 0:12professor of chemistry at Elon
4. 0:13University today I'll be taking you
5. 0:15through the appropriate procedure and
6. 0:17technique for diluting a solution a
7. 0:19common laboratory technique is preparing
8. 0:21a more dilute solution from a
9. 0:23concentrated stock
10. 0:25solution in this case we are going to
11. 0:28prepare a250 L solution of 0.01 mol we
12. 0:34know our stock solution has a
13. 0:35concentration of 250 molar the first
14. 0:39thing we need to do is determine the
15. 0:41exact number of moles in our dilute
16. 0:43solution we know our concentration needs
17. 0:46to be 01 molar or 01 moles per liter
18. 0:50since we know our number of moles per
19. 0:52liter and we know the volume we need we
20. 0:55can calculate that we need exactly
21. 0:58025 moles of sodium
22. 1:01chloride knowing our stock solution
23. 1:03contains .25 moles per liter we can take
24. 1:07the number of moles needed in our dilute
25. 1:09solution and divide by the concentration
26. 1:11of our stock solution to calculate the
27. 1:14exact number of milliliters that must be
28. 1:16transferred into our new solution in
29. 1:19this case 01 L of sodium chloride
30. 1:22solution or 10
31. 1:24m this is the stock solution of sodium
32. 1:27chloride that we will be diluting make
33. 1:29sure to pour the stock solution into
34. 1:31another container before inserting the
35. 1:33pipet into the solution this is because
36. 1:36you do not want to contaminate your
37. 1:37stock solution in this case I'm using an
38. 1:40Erland Meer flask notice that I have
39. 1:43clearly labeled the flasks to adhere to
40. 1:45proper laboratory safety protocol to
41. 1:48prepare our dilute solution we will take
42. 1:50a 10ml aliquat of our stock solution
43. 1:53using a 10ml volumetric pip head to use
44. 1:57the PIP head place the PIP head in the
45. 1:59liquid to be collected squeeze the pipet
46. 2:02bulb and allow the liquid to rise up the
47. 2:05pipet you should allow the liquid to
48. 2:07pass the line marked on the pipet but
49. 2:09before the bulb remove the bulb and
50. 2:12place your other thumb over the end
51. 2:14creating a seal and slowly release just
52. 2:16the corner of your thumb allowing the
53. 2:18liquid to exit so that the meniscus is
54. 2:21directly on the line marked on the pipet
55. 2:24this takes some practice and you may
56. 2:25need to use the bulb to pull more liquid
57. 2:27into the pipe head again never pipet by
58. 2:30mouth once you have the exact amount of
59. 2:32liquid required in the pipet hold your
60. 2:35thumb firmly over the end and transfer
61. 2:37the pipet to a new volumetric flask in
62. 2:40this case a clean 250ml volumetric flask
63. 2:43allow all of the liquid to flow out of
64. 2:45the pipet do not use the bulb to force
65. 2:48the liquid out as pipets are designed to
66. 2:50deliver the exact amount of liquid and
67. 2:53there may be a small amount of liquid
68. 2:54remaining at the end remove the pipet
69. 2:57and follow the same procedure as before
70. 2:59filling the volumetric flask with
71. 3:01solvent again monitoring the meniscus
72. 3:04until the exact volume is reached you've
73. 3:06now learned how to prepare a dilute
74. 3:08solution from a stock solution to see
75. 3:10how to prepare a stock solution you can
76. 3:12view our solution preparation video at
77. 3:15carolina.com
78. 3:17svideo everything you need to perform
79. 3:19this technique in your lab is available
80. 3:21from Carolina visit us at Carolina
81. 3:23chemistry.com to see our complete line
82. 3:26of products and kits for chemistry
83. 3:29[Music]