Concentration = # of fish

volume (L)Concentration =

V = 1000 mL

n = 2 fish

Concentration = 2 “fishar”

V = 1000 mL

n = 4 fish

[ ] = 4 “fishar”

V = 5000 mL

n = 20 fish

[ ] = 4 “fishar”

1 fish

1 (L)

Concentration = 1 “fishar”

V = 1000 mL

n = 2 moles

Concentration = 2 molar

V = 1000 mL

n = 4 moles

[ ] = 4 molar

V = 5000 mL

n = 20 moles

[ ] = 4 molar

Concentration = # of moles

volume (L)V = 250 mL

n = 8 moles[ ] = 32 molar

Making Molar

Solutions

…from liquids(More accurately, from stock solutions)

Concentration…a measure of solute-to-solvent ratio

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

“watery”

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

Making a Dilute

SolutionTimberlake, Chemistry 7th Edition, page 344

initial solution

removesample

diluted solution

same number ofmoles of solutein a larger volume

mix

moles ofsolute

Concentration“The amount of solute in a solution”

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

M = mol L

% by mass – medicated creams% by volume – rubbing alcohol

ppm 1 inch in 16 miles

ppb 1 inch in 16,000 miles

ppt 1 sec = 32,000 years

Glassware

precise; expensive

Range:

Glassware – Precision and Costbeaker vs. volumetric flask

When filled to 1000 mL line, how much liquid is present?

beaker 5% of 1000 mL = 50 mL

volumetric flask1000 mL + 0.30 mL

950 mL – 1050 mL 999.70 mL– 1000.30 mL

imprecise; cheap

Range:

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

1000 mL + 5 mL Range = 1000 mL + 5 mL 475 – 525 mL

~ ~ ~ ~ ~ ~ ~ ~

water ingrad. cyl.

mercury ingrad. cyl.

Measure to part of meniscus w/zero slope.

Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

How to mix solid chemicalsLets mix chemicals for the upcoming soap lab. We will need 1000 mL of 3 M NaOH per class.

How much sodium hydroxide will I need, for five classes, for this lab?

M = mol L 3 M =

? mol 1 L

? = 3 mol NaOH/class

How much will this weigh?

1 Na @ 23g/mol + 1O @ 16g/mol + 1 H @ 1 g/mol

MMNaOH = 40g/mol

40.0 g NaOH1 mol NaOH

X g NaOH = 15.0 mol NaOH =

To mix this, add 120 g NaOH into 1L volumetric flask with ~750 mL cold H2O. Mix, allow to return to room temperature – bring volume to 1 L.

FOR EACH CLASS:

x 5 classes15 mol NaOH

600 g NaOH

How to mix a Standard Solution

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

Wash bottle

Volume marker(calibration mark)

Weighedamount of solute

How to mix a Standard Solution

http://www.chem.ucla.edu/~gchemlab/soln_conc_web.htm

Process of Making a Standard Solution from Liquids

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

How to mix a dilute solution from a concentrated stock solution

Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

Identify each volume to two decimal places(values tell you how much you have expelled)

4.48 - 4.50 mL 4.86 - 4.87 mL 5.00 mL

Reading a pipette

www.chalkbored.com

Dilution of Solutions

Solution GuideFormula

WeightSpecific Gravity

MolarityReagent

Percent

To Prepare 1

Liter of one molar

Solution

Acetic Acid Glacial (CH3COOH) 60.05 1.05 17.45 99.8% 57.3 mL

Ammonium Hydroxide (NH4OH) 35.05 0.90 14.53 56.6% 69.0 mL

Formic Acid (HCOOH) 46.03 1.20 23.6 90.5% 42.5 mL

Hydrochloric Acid (HCl) 36.46 1.19 12.1 37.2% 82.5 mL

Hydrofluoric Acid (HF) 20.0 1.18 28.9 49.0% 34.5 mL

Nitric Acid (HNO3) 63.01 1.42 15.9 70.0% 63.0 mL

Perchloric Acid 60% (HClO4) 100.47 1.54 9.1 60.0% 110 mL

Perchloric Acid 70% (HClO4) 100.47 1.67 11.7 70.5% 85.5 mL

Phosphoric Acid (H3PO4) 97.1 1.70 14.8 85.5% 67.5 mL

Potassium Hydroxide (KOH) 60.05 1.05 17.45 99.8% 57.3 mL

Sodium Hydroxide (NaOH) 40.0 1.54 19.4 45.0% 85.5 mL

Sulfuric Acid (H2SO4) 98.08 1.84 18.0 50.5% 51.5 mL

MConc.VConc. = MDiluteVDilute

DDCC VM VM

L) (25.00 M 0.500 )(V M 14.8 VM VM C DDCC

C = concentrateD = dilute

Dilutions of Solutions

Dilution Equation:

Concentrated H3PO4 is 14.8 M. What volume of concentrate

is required to make 25.00 L of 0.500 M H3PO4?

VC = 0.845 L = 845 mL

Acids (and sometimes bases) are purchased in concentrated form (“concentrate”) and are easilydiluted to any desired concentration.

**Safety Tip: When diluting, add acid or base to water.**

Be sure to wear your safety glassessafety glasses!

1. Measure out 0.845 L of concentrated H3PO4 .

2. In separate container, obtain ~20 L of cold H2O.

3. In fume hood, slowly pour [H3PO4] into cold H2O.

4. Add enough H2O until 25.00 L of solution is obtained.

How would you mix the above solution?

Yes;we’re OK.

You have 75 mL of conc. HF (28.9 M); you need 15.0 L of 0.100 M HF. Do you have enough to do the experiment?

>2.1675 mol HAVE 1.50 mol NEED

MCVC = MDVD

28.9 M (0.075 L) = 0.100 M (15.0 L)

2211 VMVM

Dilution

• Preparation of a desired solution by adding water to a concentrate.

• Moles of solute remain the same.

Dilution

• What volume of 15.8M HNO3 is required to make 250 mL of a 6.0M solution?

GIVEN:

M1 = 15.8M

V1 = ?

M2 = 6.0M

V2 = 250 mL

WORK:

M1 V1 = M2 V2

(15.8M) V1 = (6.0M)(250mL)

V1 = 95 mL of 15.8M HNO3

Preparing Solutions

How to prepare 500 mL of 1.54 M NaCl solution

– mass 45.0 g of NaCl– add water until total volume is

500 mL 500 mLvolumetric

flask500 mL

mark

45.0 g NaClsolute

500 mLvolumetric

flask

Preparing Solutions

500 mL of 1.54M NaCl

500 mLwater

45.0 gNaCl

– mass 45.0 g of NaCl– add water until total volume is

500 mL

– mass 45.0 g of NaCl– add 0.500 kg of water

500 mLmark

1.54m NaCl in 0.500 kg of water

molality molarity