Review Chapter 2

MW – Molecules and Solutions

1- What is a Molecule? pg 40

• A molecule is a group of two or more chemically bonded atoms.

Ex: H2O, CO2, NH3.... Etc.

• They look for stability.... Octet rule Ex:

F Ne so we saw that F has a tendency to gain 1 electron

C

1.1 – Ions pg 42

Ex: Bohr-Rutherford model for Mg...

12p+ 12n

Mg+2

(+12) protons

+ (-10) electrons

+2

2 – Properties of Solution pg 50

A SolutionSolution is a homogeneous mixture whose component substances cannot be distinguished, even with the aid of a magnifying instrument.

2.2 – Concentration pg 52

• The measure of the amount of solute that is dissolved in a given amount of solution.

• Remember!Solution = Solvent + Solute

Units:Solute: mass (i.e. grams)Solvent: volume (i.e. mililitres)Concentration: g/L, %m/V, %v/v, %m/m, ppm

____________________________________________________________

(g)

(L)

Concentration in grams per litre (g/L)

C (g/L) = mass of solute (g) volume of solution (L)

Ex: If I have 500ml of coffee and I want it to have a concentration of 5g/L, how much sugar must I add to the solution?

C

m

C V

Concentration in Mass/Volume %

• Remember, the volume of the solution is equal to the volume of the solvent plus the volume of the solute

• %m/v = mass of solute x 100 volume of the solution

%m/v = mass of solute x 100 volume of the solution

Ex: If I have a 14%m/v concentrated solution in 300ml of solution, how much solute do I have?

Ex: If I have an 8%m/v concentrated solution with 5g of solute, how much solvent do I need?

Concentration in volume percent %

• Here, we are dealing only with volume

• Volume % = volume of solute x 100 (volume of solute + volume of solvent)

Ex: an 83% concentrated solution of coffee contains 100ml of creamer. How much black coffee was there to begin with?

Concentration in Mass percent %

• Here, we are dealing only with mass

• Mass % = mass of solute x 100 mass of solute + mass of solvent

Ex: if you find 36mg of dirt in 10g of Kool-Aid powder, what concentration in percent mass of your drink mix is contaminated?

Concentration in ppm

• This is used when measuring a very small amount of solute in a large amount of solvent.

• 1ppm = 1mg/1Kg or 1mg/L

• Ex: A 7.8kL swimming pool contains 0.00056g of chlorine. What is the concentration in ppm of chlorine in the swimming water?

Dilutions pg 52

1 1 2 2C V C V

Where:

C1 is the concentration of the ORIGINAL solution in g/L or % or ppm,

V1 is the volume of the ORIGINAL solution in L

C2 is the concentration of the NEW solution in g/L or % or ppm

V2 is the volume of the NEW solution in L

Ex: You want to make a 450ml solution of Kool-Aid using 34 ml of a 3.7g/L concentrated solution. What will be the concentration of the solution you’re going to make?

1)List your variable!2)Write down the formula!!3)Plug the variables into the formula!!!4)Solve for the missing variable!!!!

1 1 2 2C V C V

• Ex: I’m making juice from a 7.8g/L frozen can. I want to make a 5.3g/L solution. I add three cans of water to my juice (each can measures 500ml).

1 1 2 2C V C V

Electrical Conductivity pg 55

• What is an electrolyte?

• What is electrolytic dissociation?

NaCl(s) Na+(aq) + Cl-

(aq)

vs.

C12H22O11(s) C12H22O11(aq)

Electrolysis...

The electrode called the AnodeAnode is considered to be the positivepositive end.

The electrode called the CathodeCathode is considered to be the negativenegative end.

Types of Electrolytes pg 58

Acids have a sour taste, turns litmus paper red, and are found in many fruit juices and soft drinks. Ex: HCl H+ and Cl-

Acids are substances that release H+ ions in an aqueous solution.

Types of Electrolytes

Bases have a bitter taste, feel slippery to the touch, and are found in many cleaning products. They also turn litmus paper blue.

Ex: NaOH Na+ and OH-Ex: NH3 + H2O NH4

+ + OH-

Bases are substances that release OH- ions in an aqueous solution.

Types of Electrolytes

Salts they enhance the taste of food and do not change the colour of litmus paper. They are soluble in water and dissolve into ions.

Ex: NaCl Na+ and Cl-Ex: CaCl2 Ca2+ and 2Cl-

Salts are substances produced by the chemical bonding of a metallic ion and a non-metallic ion (other than H+ and OH- ions).

pH pg 60

“The Power of Hydrogen”

pH = - pH = - log[Hlog[H++] ]

Example…

• What is the pH of a solution who’s concentration of H+ ions is 7.93 x 10-7 ?

pH = - log [H+]pH = - log [7.93 x 10-7]

pH = 6.10

Would this be Acidic or Basic? Weakly Weakly AcidicAcidic