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: H 2 O, CO 2, NH 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 Solution A Solution 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 CV

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 g of chlorine. What is the concentration in ppm of chlorine in the swimming water?

Dilutions pg 52 Where: C 1 is the concentration of the ORIGINAL solution in g/L or % or ppm, V 1 is the volume of the ORIGINAL solution in L C 2 is the concentration of the NEW solution in g/L or % or ppm V 2 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!!!!

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).

Electrical Conductivity pg 55 What is an electrolyte? What is electrolytic dissociation? NaCl (s)  Na + (aq) + Cl - (aq) vs. C 12 H 22 O 11(s)  C 12 H 22 O 11(aq)

Electrolysis... Anode positive The electrode called the Anode is considered to be the positive end. Cathode negative The electrode called the Cathode is considered to be the negative 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: NH 3 + H 2 O  NH 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: CaCl 2  Ca 2+ 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 = - log[H + ]

Example… What is the pH of a solution who’s concentration of H + ions is 7.93 x ? pH = - log [H + ] pH = - log [7.93 x ] pH = 6.10 Would this be Acidic or Basic? Weakly Acidic