How to mix a Standard Solution

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 480

Process of Making a Standard Solution from Liquids

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 483

Markings on Glassware

TC 20oC “to contain at a temperature of 20 oC”

TD “to deliver” Ts “time in seconds”22

500 mL + 5% Range = 500 mL + 25 mL 475 – 525 mL

Beaker

Graduated Cylinder

Volumetric Flask 500 mL + 0.2 mL Range = 499.8 – 500.2 mL

Concentration…a measure of solute-to-solvent ratio

concentrated dilute “lots of solute” “not much solute”

“watery”

Add water to dilute a solution; boil water off to concentrate it.

Lmol

M

mol

L M

A. mass % = mass of solute mass of sol’n

B. parts per million (ppm) also, ppb and ppt-- commonly used for minerals or contaminants in water supplies

C. molarity (M) = moles of solute L of sol’n

-- used most often in this class

D. molality (m) = moles of solutekg of solvent

KCl m 3.30 L 2.38kg 7.85

nsol' L

solute kg m

112212 OHC m 0.055 L 0.450kg 0.0248

nsol' L

solute kg m

7.85 kg KCl are dissolved in 2.38 L of solution.

Find molality.

24.8 g table sugar (i.e., sucrose, C12H22O11) are mixed into 450 g

water. Find molality.

WRONG

mol 1culem' 10 x6.02

g 18mol 1

mL 1g 1

L 1mL 1000

L 1000 OH culem'X 23

2

OH culem' 10 x3.34F atomsX

OH culem' 1,000,000

F atom 1.5

228

2

222222 CaFc m' 10 x2.505

F at. 2CaFc m' 1

times F at. 10 x5.01 X

22322

2 CaF g 3.25 mol 1

g 78.1

cm' 10 x6.02mol 1

c m' 10 x2.505 CaF gX

What mass of CaF2 must be added to 1,000 L of water

so that fluoride atoms are present at a conc. of 1.5 ppm?

= 3.34 x 1028 m’cules H2O

NaOH g 135 mol 1

g 40.0 mol 3.38 NaOH g X

243243 )(POMg g 889 mol 1

g 262.9 mol 3.38 )(POMg g X

How many moles solute are required to make 1.35 L of 2.50 M solution?

mol = M L = 2.50 M (1.35 L) =

B. What mass magnesium phosphate is this?

A. What mass sodium hydroxide is this?

mol

L M

3.38 mol

Ba(OH) M 0.061 L 5.65

Ba(OH) g 171.3Ba(OH) mol 1

Ba(OH) g 6.58

M X 22

22

Find molarity if 58.6 g barium hydroxide are in 5.65 L solution.

mL 76.3 L 1mL 1000

L 0.763 M 0.140

g 101.1mol 1

KNO g 8.10

L X3

You have 10.8 g potassium nitrate. How many mL of solution will make this a 0.14 M solution?

convert to mL

ConcentrationConcentration

The amount of solute in a solution.

Describing Concentration

• % by mass - medicated creams

• % by volume - rubbing alcohol

• ppm, ppb - water contaminants

• molarity - used by chemists

• molality - used by chemists

MolalityMolality

solvent ofkg

solute of moles(m)molality

mass of solvent only

1 kg water = 1 L waterkg 1

mol0.25 0.25m

http://www.unit5.org/christjs/tempT27dFields-Jeff/

Solutions1.htm

Molarity of Solutions

Molarity of Solutions

Molarity of Solutions