Moles and Solutions

Counting Units Pair Trio Quartet 6-pack Dozen Baker’s dozen Score Gross 2 3 4 6 12 13 20 144

Titan Lab Created a counting unit for convenience. This is a similar process to what we do for molecules Molecules are very small Need a very big counting unit

Titan Lab How can we figure out how many Cheerios are in a box without counting them? 4

Counting Large Numbers How long would it take to count to 1 million if you counted one number each second? 5

Counting Large Numbers How long would it take to count to 1 billion if you counted one number each second? 6

Counting Unit for Molecules The mole Abbreviated mol Defined in terms of two different units Masses of atoms Measured in amu Masses of things that are convenient to measure Measured in grams

Moles Define the mole in a similar way to the titan The mass of 1 atom in amu is equal numerically to the mass of 1 mole of atoms in grams. Where 1 amu = 1.66054 x 10-27 kg

Moles How many things are in one mole? Exact same process as Titan lab

Moles 1 mol is 6.022 x 1023 items. 1 mol of doughnuts is? 6.022 x 1023 doughnuts 1 mol of quizzes? 6.022 x 1023 quizzes 1 mol of dollar bills? 6.022 x 1023 dollar bills

Moles are Huge Counting Units How many years would it take to spend 1mol of dollar bills? Assume you could spend $1 million every second of your life

Moles are Huge Counting Units Could 1 mol of basketballs cover the Earth? With a depth of 50 miles How big would 1 mol of grapefruits be? About the size of the Earth How many human cells are on Earth? About 1 mole of human cells How many moles of sand grains are in the Sahara desert? About 2 moles of sand grains

Moles Are Huge Counting Units What is the volume of 1 mol of water molecules? 18.01mL Moles are huge counting units because molecules are so tiny.

How do we count moles? Remember how we determined the number of things in a mole… Consider carbon The average mass of 1 carbon atom is? 12.01amu The mass of 1 mole of carbon atoms is? 12.01g

Conversion Factors Molar mass – the mass of 1 mole of atoms in grams Found on periodic table Numbers on periodic table are The average mass of 1 atom in amu The mass of 1 mole of atoms in grams Mass on periodic table in grams = 1 mol Avogadro’s number – 6.022x1023 things Found on reference table 1 mol = 6.022x1023 things

Practice Problems How many carbon atoms are in 5.10 mol of carbon? What is the mass of 5.10 mol of carbon?

Practice Problems What is the mass of 2.50mol of water? How many water molecules are in 2.50mol of water?

Practice Problems What is the mass of 1.89x1024 molecules of ammonia? How many formula units of calcium chloride are in 18.5g of calcium chloride?

Solutions

Solutions Solution – a homogeneous mixture of two or more compounds. Homogeneous – looks the same throughout, mixed at the molecular level Solvent – the compound that is the majority of a solution, the compound that is doing the dissolving Solute – the compound that there is less of in a solution, what got dissolved in the solvent. Can be more than one solute in a solution Can only be one solvent

Different Solutions Solid Dissolved in a Liquid Salt Water Liquid Dissolved in a Liquid Rubbing Alcohol (isopropanol in water) Gas Dissolved in a Liquid An unopened Pepsi Gas Dissolved in a Gas Air Solid Dissolved in a Solid Alloys

Concentration Need to be able to tell how much compound is dissolved in a solution. Molarity – M – moles of solute per liter of solution In equations, a molarity of a specific substance maybe represented using square brackets Ex. [NH3] = 0.100M

Practice Problems What is the molarity of a solution made by dissolving 0.125mol of sodium hydroxide in enough water to make 500.0mL of solution?

Practice Problems What volume of 18.0M sulfuric acid is required to obtain 0.0500mol sulfuric acid?

Practice Problems How many moles of iron(II) sulfate are in 125mL of a [FeSO4] = 0.0530M solution?

Practice Problems 15.5g of barium chloride is dissolved in enough water to make 150mL of solution. What is the concentration of barium chloride?

Practice Problems What volume in L of a 0.100M ammonia solution contains 4.95x1023 ammonia molecules?

Practice Problems What mass of glucose is dissolved in 2.00L of a [C6H12O6]=0.05M solution?

Practice Problems What volume in L of a 0.100M ammonia solution contains 4.95x1023 ammonia molecules? What mass of glucose is dissolved in 2.00L of a [C6H12O6]=0.05M solution?

Practice Problems What volume of a 0.150M solution of aluminum nitrate is required to obtain 5.00g of aluminum nitrate? How many formula units of titanium(IV) oxide are in 10.0g of titanium(IV) oxide?

Solubility

Electrolytes What type of compounds are electrolytes? Why are ionic compounds electrolytes? Consider sodium chloride: Is this an electrolyte? Why? Consider sucrose (sugar, C12H22O11): Consider calcium carbonate:

Electrolytes Why is calcium carbonate NOT an electrolyte? Not all ionic compounds are soluble in water. In some compounds the attractions between the ions is too great to allow them to be separated.

Solubility Rules Located in your reference table A compound that is soluble will dissolve in water A compound that is insoluble will “not” dissolve in water Solubility is really a sliding scale Notice the solubility rules have a cutoff of 0.1M Anything that can produce a solution of 0.1M or greater is soluble Anything that cannot produce a solution of 0.1M is “insoluble.”

Practice Are the following soluble or insoluble in water? Sodium iodide Iron(III) carbonate Silver sulfate Calcium sulfide Potassium phosphate

Solubility Curve Remember everything has a different solubility in water. Some things are hardly soluble at all “Insoluble” Some things are much more soluble This is shown with a solubility curve Shows the maximum amount of solute that can dissolve

Trends in Solubility Most solids are more soluble as temperature increases Most gasses are more soluble as temperature decreases. Gas solubility can be increased by adding pressure to a liquid.

How do we describe solutions? Concentrated – has lots of solute dissolved in it Dilute – doesn’t have a lot of solute dissolved in it.

How do we describe solutions? Saturated solution – a solution that can NOT dissolve more solute. At capacity Unsaturated solution – a solution that can dissolve more solute. Not yet at capacity

What the heck is “Supersaturated?” Supersaturated solution – when a solution has more solute dissolved than it should Over capacity NOT stable Nucleation site – some imperfection that allows the excess solute in a solution to leave the solution Mentos in Diet Coke http://www.eepybird.com/

How is a supersaturated solution made? Initially make a traditional saturated or unsaturated solution Change the conditions on the solution so that it is then supersaturated. Dissolve lots of solute in hot water and then cool the hot water. Dissolve carbon dioxide at high pressure and then release the pressure.

Dilution

A Real World Problem I need 500.0mL of 1.0M hydrochloric acid. I only have 12.0M hydrochloric acid… How do I make the solution that I need? Take some of the 12.0M HCl and dilute it out with water.

How much do I dilute? How many moles of HCl need to be dissolved in the dilute solution? Where are these moles of HCl going to come from?

How much do I dilute? What volume of concentrated solution do I need to get that number of moles?

Combine it all together

Practice Problems What volume of 12.0M HCl is needed to make 500.0mL of a 1.0M HCl solution?

Practice Problems I have roughly 750mL of 12.0M HCl left for the year. How much 6.0M HCl can I make?

Practice Problems What is the concentration of a solution prepared by mixing 10.0mL of 18.0M H2SO4 in enough water to make 0.5000L of solution?

Practice Problems A solution of iron(III) nitrate is prepared by taking 5.0mL of a stock solution of unknown concentration and diluting it to 2.00L. This solution is later found to have a concentration of 0.0112M. What is the concentration of the unknown stock solution?

Practice Problems I found an unlabeled solution of nitric acid in my acid cabinet when I came to West. I took 10.0mL of the unknown solution and diluted it to 1.00L. I then titrated that solution and determined its concentration to be 0.065M. What is the concentration of the unlabeled solution?

Counting Atoms

Practice Problem How many hydrogen atoms are in 5.50x1023 water molecules?

Practice Problems What mass of carbon dioxide is needed to obtain 4.50x1022 atoms of oxygen?

Practice Problems How many sulfur atoms are found in 3.55g of iron(III) sulfide?

Practice Problems What volume (in mL) of 0.34M sucrose solution (C12H22O11) contains 1.50x1023 carbon atoms?

Practice Problems How many mL of 0.525M calcium chloride are needed to obtain 5.00x1022 chloride ions? What is the molarity of a solution prepared by dissolving 36.05g of sodium hydroxide in 3.00L of water? What is the mass of ammonia dissolved in 100.0mL of a 14.8M ammonia solution? What mass of aspirin (C9H8O4) contains 1.00x1023 atoms of oxygen? What is the [HCl] of a solution prepared by dissolving 15.0mL of 12.0M hydrochloric acid in enough water to make 0.50L of solution?

How many sodium ions are dissolved in 5. 00mL of a 0 How many sodium ions are dissolved in 5.00mL of a 0.100M sodium sulfate solution?