Making_Solutions - Andreas Help Sheet on Preparing...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Andrea’s Help Sheet on Preparing Solutions There are several types of stock solutions made in the research lab: Percent (%) solutions, Molar (M) solutions, X solutions, and mg/ml solutions. First are instructions on how to make % solutions. First, know the definition of a % solution: 1% = 1g/100ml That’s the basic formula, and it is logical because “per cent” means “per hundred”. So, let’s say you are assigned the task of making 1 liter of 20% SDS stock solution, a lab basic. (On quizzes, you may be told the MW of the chemical; it is not used in % solutions, so ignore it.) The three steps are: 1: write out the formula: 1% = 1g/100ml 2: scale it up on the percentage: 20% = 20g /100ml 3: scale to the final volume by multiplying by 10: 20% = 200g/1000ml Write out the description in the following manner: Place 200g of SDS powder a 1L beaker and add H 2 O up to 900ml. When dissolved, transfer solution to a 1L graduated cylinder and add H O to 1000ml. This works whether for a % w/v solution (as exampled above) or a % v/v solution. Suppose you need 100ml of 20% EtOH: 1% = 1ml/100ml 20% = 20ml/100ml Mix 20ml EtOH with 80ml H O for a final volume of 100ml. Next, let’s look at Molar (M) solutions. First, know the definition of a Molar solution: 1M = 1MW(in grams)/Liter (MW = molecular wt.) That’s the basic formula, and is logical because Molar is defined as a solution concentration having one mole of solute per liter of solution. So, lets say you are assigned the task of making 100ml of 5M NaCl . Here, you will need the molecular wt for NaCl; it is 58.44. The three steps are: 1: write out the formula: 1M = 1MW(g)/1000ml 2: plug in the numbers & scale it up on the Molarity: 5 M = (58.44)g /1000ml & work out the calculations: 5M = 292.2g/1000ml 3: scale to the final volume by dividing by 10: 5M = 29.22g/100ml Write out the description in the following manner: Dissolve 29.22g of NaCl in 90ml H O in a 100ml beaker. Transfer solution to a 100ml graduated cylinder and add H O to 100ml.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 10/07/2010 for the course BCHS BCHS 3304 taught by Professor Legge during the Spring '09 term at University of Houston.

Page1 / 3

Making_Solutions - Andreas Help Sheet on Preparing...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online