Making Solutions
An important part of doing research, from the most simplistic topic to the most complex, is running labs and conducting experiments. Within these labs, the research must be able to create an experiment which involves deciding what a problem, purpose a hypothesis, develop methods and procedures on how to test the hypothesis, collect data, examine the data and come up with some type conclusion based on the information gathered. The preparation of the majority of these lab experiments and research involve making chemical solution. These chemical solutions are made based in the weight and volume of these chemicals.
For most experiments, the chemicals that are being used have to be in chemical form. There are several different ways to prepare solutions:
1. Simple Dilution- a unit volume of a liquid material of interest is combined with a volume of a solvent to create a concentration.
2. Mixing parts or volumes- mixing x amount of one unit with x amount of volumes of water
3. Serial Dilution- a series of dilutions that enhance the dilution factor quickly starting with a small initial quantity of material.
Formula= (DF)= DF1 x DF2 X DF3......
4. Making fixed volumes from liquid reagents- making a desired concentration using a specific known concentration
Formula: VC1C1 = V2C2
5. Molar solutions- useful in chemical reaction calculations because they directly relate the moles of solute to the volume of solution.
Formula= desired volume x desired molarity x molecular weight
6. Percent solutions- many reagents are mixed as percent concentrations. Useful when working with a dry chemical
Formula= weight x desired final volume / 100
7. Molarity
Formula= percent of solution x 10
molecular weight
Solute - substance that dissolves in a solution
Solvent - substance that dissolves another to form a solution.
Solution - A mixture of two or more pure substances.
Mole - A fundamental unit of mass (like a "dozen" to a baker) used by chemists. etc)
Avogadro's number- 6.02 x 1023 molecules of that substance. Equal to one number
Graduated cylinder- is a common piece of laboratory equipment used to measure the volume of a liquid.
electronic scale-a scale for weighing
pipette- slender tube attached to or incorporating a bulb, for transferring or measuring out small quantities of liquid, especially in a laboratory.
weigh boats- are constructed of rubberized polystyrene, making them easy to handle and flexible.
beaker- tool to weigh volume
Vocabulary
Important tools
1. Suppose you have 3 ml of a stock solution of 100 mg.ml ampicillin (C1) and you want to make 200 ul (C2) of solution having 25 mg.ml (V2). Find volume (V1) of the stock to use as part of the 200 ul total volume needed.
Covert 200 ul to mll= 0.2 ml
V1C1=V2C2
V1= V2C2/ C1
V1= (0.2 ml x 25 mg/ml)/ 100 mg/ml
v1= 0.05 ml= 50 ul
2. Prepare a liter of a simple molar solution from a dry reagent
Chemical Formula Weigh of dry reagent = 194.3 g/ mole used to make 0.15 M solution
M x W= 194.3 g/mole x 0.15 moles/ L= 29.145 g/L
3. A chemical has a FW of 180 g/mole and you need to make up 25 ml (0.025 L) of 0.15 M (m=moles/L) solution. How many grams of the chemical must be dissolved in 25 ml water to make this solution
grams/ desired volume (L)= desired molarity (mole/L) x FW(g/mole)
0.025 : x 0.15 mole/L x 180 g/mole