Experiment 0: Pipetting And Diutions

Question 1

Define Solution

Answer 1

A mixture of a compound (solute) in a liquid (solvent). The amount (mass) of the compound in the total volume of solution is the concentration of the solute. A solution can have more than one compound and each compound has a concentration.

Question 2

What is the equation for concentration and what are some common units?

Answer 2

Concentration= Mass/ Total Volume

Mass in Gram/ Volume in Liters

G/L

Question 3

What is the equation for molarity?

Answer 3

Moles/Liters

Question 4

What is another way concentration is expressed?

Answer 4

As a percentage where 1 gram of solute in 10ml of solvent= 10% solution.

Question 5

How is concentration expressed in Biology?

Answer 5

X.
A 1X solution is ready for use, while a 10X stock solution needs to be diluted 10-fold or 1 part solution to 9 parts of solvent. The solvent is almost always water in biology.

Question 6

How is concentration calculated?

Answer 6

Concentration is always calculated using the total or final volume. If two solutions are mixed, the final volume is the sum of them. For example, if 1 liter of solution is mixed with 4 liters of solution two, the final volume is 5 liters, and 5 liters is used in the calculation below.

Question 7

How do dry reagents act with respect to solutions upon dissolving?

Answer 7

When making a solution starting from a dry reagent, the reagent will add to the volume upon dissolving. Thus, a 100 mL solution of NaCl may have only 80 ml of water, but after dissolution, salt will increase the volume to 100 ml.

Question 8

In molecular biology labs, we use volumes in the range of _____ to _____.

Answer 8

Microliters-Liters

Question 9

Solutions are often supplied as _____ that have to be diluted with water before use.

Answer 9

Concentrates (stock solutions).

Question 10

Stock solutions are given names that refer to just how _____ they are.

Answer 10

Concentrated.

For example, a stock solution that is 10-fold concentrated is known as a 10X solution. A 10X Solution needs to be diluted 10-fold to a 1X solution prior to use.

Question 11

What formula is used to calculated a dilution?

Answer 11

C1V1=C2V2

If a solution requires multiple reagents being mixed together, the volume of each reagent is calculated using the dilution formula. These volumes are added and subtracted from the total to determine the volume of water needed to complete the new solution.

Question 12

Micro pipetas are used to measure _____ volumes.

Answer 12

Microliter.

Question 13

What are the volume ranges of the 4 micropipettes?

Answer 13

P2 0.5-2
P20 2-20
P200 20-200
P1000 200-1000