Review

A solution is a homogeneous mixture.The solvent is the major component of the

solution.The solute is the minor component and active

ingredient.A saturated solution holds the maximum

amount of solute that is theoretically possible for a given temperature.

Solution Concentration

Is one glass of tea stronger than the other?– What’s true about the “stronger” glass of tea?– How much tea does it have in it compared to

the other glass?

Concentrated vs. Dilute

How do we know how strong a solution is?Concentrated – LOTS of solute, little solventDilute – little solute, lots of solvent

Concentrated and dilute are not quantitativeMeasurements are needed to get precise

data

Concentrated vs. Dilute

Concentrated solution

Dilute solution

= solute particles

Solution Concentration

Concentration – a ratio comparing the amount of solute (the part) to the amount of solution (the whole).

Concentration is expressed by:– % by weight (% w/w)

– Mass of solute x 100 Mass of solution

– % by volume (% v/v)– Volume of solute x 100

Volume of solution

Solution Concentration

• parts per million (ppm) or parts per billion (ppb) for very low concentrations• Mass of solute x 1,000,000 Mass of solution

• molality (m)• Moles of solute Mass(kg) of solution• Used for high-concentration solutions or where

temperature changes significantly

Molarity

– Molarity (M) –The most common unit of concentration in chemistry

– Unit = moles per liter (mol/L)– Or just M

Formula:

– Example: 1.500 mol/L = 1.500 M– read as “1.500 Molar”

solution of Liters

solute of moles Molarity

Molarity

What is the Molar concentration of a sol’n if 0.198 mol KNO3 is dissolved in enough water to make 0.800 L?

M 0.248L 0.800

KNO mol 0.198 Molarity 3

Molarity

What is the Molar concentration of a sol’n if 292 grams of NaCl (MM = 58.44 g/mol) is dissolved in enough water to make 800. mL? Convert g of NaCl to mol of NaCl

Convert mL to L

Determine Molarity

292gNaCl x 1mol NaCl 58.44g NaCl

= 5.00mol NaCl

800.mL x 1 Liter 1000mL

= 0.800L

Molarity = 5.00mol 0.800L

Molarity = 6.25M

Molarity

What is the Molar concentration of a sol’n if 10.5 grams of glucose (Molar Mass = 180.18 g/mol) is dissolved in enough water to make 20.0 mL of sol’n?

– Convert g of glucose to mol of glucose.

– Convert mL to L.

– Determine Molarity

10.5g glucose x 1mol glucose 180.18g glucose

= 0.0583mol glucose

20.0mL x 1 Liter 1000mL

= 0.0200L

Molarity = 0.0583mol 0.0200L

Molarity = 2.92M

Boiling Point Elevation & Freezing Point Depression

• Concentration affects boiling points and freezing points• The greater the concentration, the greater the effect

• Increasing concentration raises the boiling point• Adding salt to boiling pasta cooks it at a hotter temperature

• Increasing concentration lowers freezing point• Adding salt/brine to icy roads causes water to freeze at a

lower temperature, melting ice and snow• Some solutes have greater affect than others

• Ionic compounds dissociate into multiple ions, increasing the number of particles in solution

• C12H22O11(s) → C12H22O11(aq)

• NaCl(s) → Na+(aq) + Cl-(aq)

• CaCl2(s) → Ca2+(aq) + 2Cl-(aq)

1 particle

2 particles

3 particles

Normal Freezing Point

Freezing Point and NaCl Concentration

Percent by Weight

% by weight (% w/w)

What is the % w/w of a solution if 3.00 grams of NaCl are dissolved in 17.00 g of water?– mass of solute = 3.00 g

– mass of solution = 3.00 g + 17.00 g = 20.00 g

– (3.00 g / 20.00 g) x 100% = 15.0% w/w

100% x solution of mass total

solute of mass %w/w

Percent by Volume

% by volume (% v/v)

What is the % v/v of a solution if 20.0 mL of alcohol are dissolved in 50.0 mL of solution?– volume of solute = 20.0 mL

– volume of solution = 50.0 mL

– (20.0 mL / 50.0 mL) x 100% = 40.0%

100% x solution of volume total

solute of volume %v/v