Presentation on theme: "Dilution of Solutions. Concentration = # of fish volume (L) Concentration = V = 1000 mL n = 2 fish Concentration = 2 fishar V = 1000 mL n = 4 fish [ ]"— Presentation transcript:
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 Solution Timberlake, Chemistry 7 th Edition, page 344 initial solution remove sample diluted solution same number of moles of solute in a larger volume mix moles of solute
Concentration The amount of solute in a solution mol L M A. mass % = mass of solute mass of soln 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 soln – used most often in this class D. molality (m) = moles of solute kg of solvent M = mol L % by mass – medicated creams % by volume – rubbing alcohol
Want to see what taking in a milligram per kilogram of your body weight amounts to? Its the equivalent of 726 people, each weighing 150 pounds, sharing a chocolate bar (~50 grams). A part per million may be hard to comprehend or visualize. Want to see how much it is? A step in a journey of 568 miles. Or one minute in two years. Taking that further, a part per trillion is a million times smaller than that credit card on the football field, for example, or 6 feet out of a journey of six round trips to the sun (Editor's note: 95 million miles one way to the sun). Its a credit card lying in the middle of a football field.
ppm 1 inch in 16 miles ppb 1 inch in 16,000 miles ppt 1 sec = 32,000 years
precise; expensive Range: Glassware – Precision and Cost beakervs.volumetric flask When filled to 1000 mL line, how much liquid is present? beaker 5% of 1000 mL = 50 mL volumetric flask 1000 mL + 0.30 mL 950 mL – 1050 mL 999.70 mL– 1000.30 mL imprecise; cheap Range:
Markings on Glassware TC 20 o C to contain at a temperature of 20 o C TD to deliver T s time in seconds 22 500 mL + 5%Range = 500 mL + 25 mL 475 – 525 mL Beaker Graduated Cylinder Volumetric Flask 500 mL + 0.2 mLRange = 499.8 – 500.2 mL 1000 mL + 5 mLRange = 1000 mL + 5 mL 475 – 525 mL
How to mix solid chemicals Lets 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 MM NaOH = 40g/mol 40.0 g NaOH 1 mol NaOH X g NaOH = 15.0 mol NaOH = To mix this, add 120 g NaOH into 1L volumetric flask with ~750 mL cold H 2 O. Mix, allow to return to room temperature – bring volume to 1 L. FOR EACH CLASS: x 5 classes 15 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) Weighed amount 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
Identify each volume to two decimal places (values tell you how much you have expelled) 4.48 - 4.50 mL 4.86 - 4.87 mL5.00 mL Reading a pipette www.chalkbored.com
Dilution of Solutions Solution Guide Formula Weight Specific Gravity Molarity Reagent Percent To Prepare 1 Liter of one molar Solution Acetic Acid Glacial (CH 3 COOH)60.051.0517.4599.8%57.3 mL Ammonium Hydroxide (NH 4 OH)35.050.9014.5356.6%69.0 mL Formic Acid (HCOOH)46.031.2023.690.5%42.5 mL Hydrochloric Acid (HCl)36.461.1912.137.2%82.5 mL Hydrofluoric Acid (HF)20.01.1828.949.0%34.5 mL Nitric Acid (HNO 3 )63.011.4215.970.0%63.0 mL Perchloric Acid 60% (HClO 4 )100.471.549.160.0%110 mL Perchloric Acid 70% (HClO 4 )100.471.6711.770.5%85.5 mL Phosphoric Acid (H 3 PO4)97.11.7014.885.5%67.5 mL Potassium Hydroxide (KOH)60.051.0517.4599.8%57.3 mL Sodium Hydroxide (NaOH)40.01.5419.445.0%85.5 mL Sulfuric Acid (H 2 SO 4 )98.081.8418.050.5%51.5 mL M Conc. V Conc. = M Dilute V Dilute
C = concentrate D = dilute Dilutions of Solutions Dilution Equation: Concentrated H 3 PO 4 is 14.8 M. What volume of concentrate is required to make 25.00 L of 0.500 M H 3 PO 4 ? V C = 0.845 L = 845 mL Acids (and sometimes bases) are purchased in concentrated form (concentrate) and are easily diluted to any desired concentration. **Safety Tip: When diluting, add acid or base to water.**
safety glasses Be sure to wear your safety glasses! 1. Measure out 0.845 L of concentrated H 3 PO 4. 2. In separate container, obtain ~20 L of cold H 2 O. 3. In fume hood, slowly pour [H 3 PO 4 ] into cold H 2 O. 4. Add enough H 2 O until 25.00 L of solution is obtained. How would you mix the above solution?
Yes; were 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 HAVE1.50 mol NEED M C V C = M D V D 28.9 M (0.075 L) = 0.100 M (15.0 L)
One mole, in solution. What do you call a tooth in a glass of water? - A one molar solution.
Dilution Preparation of a desired solution by adding water to a concentrate. Moles of solute remain the same.
Dilution What volume of 15.8M HNO 3 is required to make 250 mL of a 6.0M solution? GIVEN: M 1 = 15.8M V 1 = ? M 2 = 6.0M V 2 = 250 mL WORK: M 1 V 1 = M 2 V 2 (15.8M) V 1 = (6.0M)(250mL) V 1 = 95 mL of 15.8M HNO 3
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 mL volumetric flask 500 mL mark 45.0 g NaCl solute
500 mL volumetric flask Preparing Solutions 500 mL of 1.54M NaCl 500 mL water 45.0 g NaCl –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 mL mark 1.54m NaCl in 0.500 kg of water molality molarity
Preparing Solutions 250 mL of 6.0M HNO 3 by dilution measure 95 mL of 15.8M HNO 3 95 mL of 15.8M HNO 3 water for safety 250 mL mark combine with water until total volume is 250 mL Safety: Do as you oughtta, add the acid to the watta!
Solution Preparation Lab Turn in one paper per team. Complete the following steps: A) Show the necessary calculations. B) Write out directions for preparing the solution. C) Prepare the solution. For each of the following solutions: 1) 100.0 mL of 0.50M NaCl 2) 0.25m NaCl in 100.0 mL of water 3) 100.0 mL of 3.0M HCl from 12.1M concentrate.