MOLE JOKES What was Avogadro's favorite Indian tribe? A: The Molehawks Why cant Avogadro have pets? A: Because he will mole them. What element do moles love to study in chemistry A: Molybdenum

Molarity More about the Mole!

Recall the meaning of the terms: Solution: Solute: Solvent: a homogeneous mixture of two or more substances. The component in a solution which exists in the smaller quantity. The component in a solution which exists in the greater quantity.

Molar Concentration: CONCENTRATION: The amount of a substance which exists in a given volume of the solution CONCENTRATED: A solution with a relatively HIGH concentration (large amount of substance dissolved in the solution). DILUTE: A solution with a relatively LOW concentration (very little substance dissolved in the solution).

Molar Concentration ( Molarity) is the number of moles of substance contained in 1L of solution. (mol/L) NOTE: The above definition states 1 L of SOLUTION not 1L of SOLVENT. Things to remember: the unit symbol for “mol/L” = “M”. the unit symbol “M” is said as “molar”. The short hand symbol for “molar concentration of...”is a set of brackets: “[...]” molar concentration = 𝐦𝐨𝐥𝐞𝐬 𝐯𝐨𝐥𝐮𝐦𝐞 c= 𝒏 𝑽

Example: If 2.0 L of solution contains 5.0 mol of NaCl, what is the molarity of NaCl(aq)? Molarity = 𝐦𝐨𝐥 𝐋 ∴[NaCl] = 𝟓.𝟎𝐦𝐨𝐥 𝟐.𝟎𝐋 = 2.5 mol/L = 2.5M

More Examples: 1. What is the [NaCl] in a solution containing 5.12 g of NaCl in 250.0 mL of solution? Answer: [NaCl] = 0.350M 2. What mass of NaOH is contained in 3.50 L of 0.200M NaOH? Answer: 28.0g NaOH

Making Solutions: Using a balance, obtain the required mass of solute in a beaker. Dissolve the solid in distilled water. Transfer the solution and rinse all equipment into a clean volumetric flask. Add distilled water up to the calibration line on the flask. An eye dropper may be used. Stopper the volumetric flask and mix the contents thoroughly. (invert 20 times)

More Examples: 3. What is the molarity of pure Sulfuric acid, H2SO4(aq), having a density of 1.839 g/mL? Answer: [H2SO4] = 18.7M 4. What is the molarity of the CaCl2 in a solution made by dissolving and diluting 15.00 g of CaCl2·6H2O to 500.0 mL? Answer: [CaCl2] = 0.1369M

Sample calculations 1. Zak dissolves 3.00 moles of HCl in 5.00 L of solution. Find [ HCl]

2. Find the [NaCI] if 25.0 g are dissolved in 62.5 L of solution

3. How many moles HCI will it take to make 250 ml of 0.32 M HCI?

4. How many mL of 0.74M NaCl solution could you make from 123g of NaCl?

MOLE JOKES What are mammoles? A: Four-legged animoles! What line from Shakespeare do high school moles have to memorize? A: "To mole or not to mole, this is the question." . Why is it bad to tell mole jokes A: It's mole-itically incorrect

Dilution Calculations: Simple dilution of a chemical in solution ci ×vi = cf ×vf Where: ci = initial concentration of solution vi = initial volume of solution cf = diluted concentration vf = diluted volume

In a diluted solution… NOT CHANGED, only the concentration. Therefore: …the amount of chemical in the solution HAS NOT CHANGED, only the concentration. Therefore: MOLES OF CONCENTRATED CHEMICAL = MOLES OF DILUTED CHEMICAL (this is why our equation works!)

Simple Dilution Example: If 200.0 mL of 0.500 M NaCl is added to 300.0 mL of water, what is the resulting [NaCl] in the mixture? ci=0.500M vi= 200.0mL cf=? vf=500.0mL ci •vi = cf •vf cf= 𝐜𝐢𝐯𝐢 𝐯𝐟 = 𝟎.𝟓𝟎𝟎𝐌 𝐗𝟐𝟎𝟎.𝟎𝐦 𝟓𝟎𝟎.𝟎𝐦𝐋 =0.200M

Mixing Solutions of the Same Chemical Together: Method A: Treat mixtures as two separate dilutions then add the results of the individual single dilutions to get the overall concentration NOTE: the final concentration should be BETWEEN the two initial concentrations!

Mixing Solutions of the Same Chemical Together: Example: If 300.0 mL of 0.250M NaCl is added to 500.0 mL of 0.100 M NaCl, what is the resulting [NaCl] of the mixture? solution 1: ci1 •vi1 = cf1 •vf1 cf1= ci1vi1 vf1 = 0.250M X300.0 𝑚𝐿 800.0mL =0.09375M solution 2: ci •vi = cf •vf cf= 𝐜𝐢𝐯𝐢 𝐯𝐟 = 𝟎.𝟏𝟎𝟎𝐌 𝐗𝟓𝟎𝟎.𝟎𝐦𝐋 𝟖𝟎𝟎.𝟎𝐦𝐋 =0.0625M Final Concentration = cf1 + cf2 = 0.09375 M + 0.0625M=0.15625 M =0.156M Answer: [NaCl]=0.156M

c final = (c1 x v1) + (c2 x v2) ( v1 + v2 ) Method B: Calculate the total number of moles (n = c x v) and divide by the total volume. c final = (c1 x v1) + (c2 x v2) ( v1 + v2 ) = 0.250M x 300.0mL+0.100x500.0mL (300.0+500.0)mL = 0.156M  

Mixing Solutions of Different Chemicals Together: The solutions dilute each other, so two dilution equations would be needed – one for each chemical present Example: What are the final [NaCl] and [KOH], if 0.280L of 0.100M NaCl are added to 575.0mL of 0.850M KOH? Answer: [NaCl] = 0.0327M [KOH] = 0.572M

MOLES LITERS OF GAS AT STP (22.4 L/mol) MASS IN GRAMS NUMBER OF Molar Volume (22.4 L/mol) MASS IN GRAMS MOLES NUMBER OF PARTICLES Molar Mass (g/mol) 6.02  1023 particles/mol Molarity (mol/L) LITERS OF SOLUTION