Working With Solutions

Question 1

Solubility

Answer 1

The maximum possible concentration of a solute at specific temperature and pressure

Question 2

Percentage concentration

Question 3

“Parts per” concentration

Answer 3

• Scientists in medical or environmental fields work with small measurements of concentration
• Making these concentrations into amount concentration or percentage concentrations gives awkward numbers to work with
• Very dilute solutions are expressed as parts per million (ppm, 1:10^6), parts per billion (ppb, 1:10^9), and parts per trillion (ppt, 1:10^12)

Question 4

Preparing solutions

Answer 4

• Many chemical reactions have aqueous solutions
• To get reliable data, the recant solutions must be carefully prepared using known concentrations
• Standard solutions are always used to start
• Standard solution: a solution in which the precise concentration is known

Question 5

Preparing solutions using volumetric flask

Answer 5

• Standard Solutions are prepared using volumetric flasks
• Frist, the known solute is dissolved in one quarter of solvent to create solution
• Then, the solvent is added until the bottom of solution meniscus touches the calibration mark
• It becomes the standard solution

Question 6

Dilution

Answer 6

• Standard solutions are sometimes too concentrated for the needed reaction
• Dilution: To reduce the concentration of the solution, more solvent is added
• Graduated pipettes are used to transfer precise volume of a liquid to achieve a desired concentration

Question 7

Calculations involving dilution

Answer 7

• The amount of moles of a solute remain constant for new solution
• N1 = n2
• n1 is the moles of solute in concentrated (original) solution = n2 is the moles of solute in diluted (new) solution
• c1V1= c2V2
• V2 is the total volume of solution, not the volume of added solvent

Question 8

Percentage concentration

Answer 8

1. Percentage volume/volume (% V/V)
   c v/v = v solute/ v solution x 100
   Good for liquid-liquid solutions
2. Percentage weight/volume ( % W/V [g/mol])
   cw/v= m solute/v solvent x 100
   Good for solid-liquid solutions
3. Percentage weight/weight (% W/W)
   c w/w = m solute/ m solvent x 100
   Good for solid-liquid or solid-solid solutions

Question 9

“Parts per” concentration formula

Answer 9

C ppm= m solute/ m solvent x 10^6
C ppb= m solute/ m solvent x 10^9
C ppt= m solute/ m solvent x 10^12