DECEMBER 14

Today in class we started the section on balancing equations. I shall finish this tomorrow once I bring my notes home.

HOMEWORK:Pg. 284 #1 & 2 , Pg 281#1-4

DECEMBER 7

Today in class we were interrupted by an earthquake!!!!.... a fake one ofcourse !
After the class got settled we quickly started our LAB :) -->DILUTION AND CREATING SOLUTIONS

Mr. Doktor gave us our last set of notes before our exam.

FINDING MOLECULAR FORMULAS
-you need the empirical formula and molar mass

Example: The empirical formula for a compound is CH2O and the molar mass is 60.0 g/mol. Find the molecular formula (work is shown below)



Example: The empirical formula for a compound is C2H6O and the molar mass is 138g/mol. Find the molecular formula. (work is shown below)

STOCK SOLUTION

--are con'c solutions from suppliers

12 M HCl

15M HNO3

18M H2SO4

Homework: STUDY FOR TEST (thursday, December 10)

WHAT DOES THE TEST CONSIST OF?

-all mole conversions<---avogadro's number

-empirical formulas

-percent mass & percent composition

-concentration

-molar volume

-dilution

-molecular formulas

December 3, 2009

Giving Directions

Making solutions ----> figure out mass to add

EXAMPLES:

A.Kristina is asked to make a 350mL solution of K2SO4 with a concentration of 0.65M. What STEPS will he follow?
V= 350mL = .350L

Molar Mass: K2SO4 = 174.3g/mol

0.65mol/L x (0.350L) = 0.2275

(o.2275mol) x 174.3g/mol = 39.65g

These are the STEPS we get when we refer to the work above:
1. Weigh 39.65 of K2SO4
2. Measure 350mL of water
3. Stir your solution


B. Give directions to make 3.00L of 5.0M NaOH.
Molar Mass: NaOH = 40g

5.0mol/L x (3.00L) = 15mol

(15mol) x 40g/mol = 600g

These are the STEPS we get when we refer to the work above:
1. Weigh 600g of NaOH
2. Measure 3.00L of water
3. Stir your solution

Dilution of Solution

When you add water the concentration decreases.
If volume is doubled, concentration is halved.



EXAMPLES:

A.Heidi adds 200.0mL of water to 60.0mL of 0.80M HCl. Find the final con'c of HCl.
C1 = 0.80M
V1 = 60.0mL
C2 = ?
V2 = 260mL

0.80M/L x (0.060L) = 0.048 mol

C1V1/V2 = C2 = (0.80)(60.0mL)/260mL = 0.18M


B. Alanna adds water to 200mL of 0.45M HF. He gets a final volume of 500mL. Find the final[HF].
C1 = 0.45M
C2 = ?
V1 = 200mL
V2 = 500mL

C1V1 = C2V2
(0.45)(0.200) = C2(0.500L)

(0.45)(0.200)/0.500 = C2

C2 = 0.10M

C. Sara dilutes 60.0mL of 0.40M HNO3 to 0.15M. What is the final volunme?

C1 =0.40M
V1 =60.0mL
C2 =0.15M
V2 =?

C1V1 = C2V2

(0.40M)(0.060L)/0.15M = V2
V2 = 0.160L = 160mL

-->How much water was added?
160mL - 60mL = 100mL

Today in class we got our mid-term results back. Afterwards we learnt about CONCENTRATION

WHAT IS A SOLUTION?

a solution is a homogeneous mixture.--> not being able to differ the different substances mixed

WHAT IS A SOLVENT?

component presented in larger component

WHAT IS SOLUTE?

the component present in the SMALLER amount.

for example: SALT in WATER. water= SOLVENT salt= SOLUTE :)

WHAT IS CONCENTRATION?

the amount of solute over the amount of solvent

(i do not have my notes with me right now, but i'll complete it tomorrow!)

- kristina

ALSO!!** don't forget.....in order to figure out the concentration or anything else, we need to know how to get MOLES. * don't forget about moles :)

ENJOY THIS VIDEO :)

homework: unit 2 homework questions 25-28

NOVEMBER 17 2009

(Heidi)

NOVEMBER 13 2009

EMPIRACAL FORMULAS

Find the total mass of Carbon in a 3.0kg sample of ethanol.
(C2H5OH)
^ ^ ^ ^
2(12) 5(1) 1(16) 1(1)=46.0g/mol

C2H6O<--Empiracal Formula Empiracal Formulas are simplest formulas Molecular Empiracal
P4H10 ------> P2H5
C1oH22 ------> C5H11
C6H18O3 ------> C2H6O
N2O4 ------> NO2
(*Think lowest common denomenator*)

Empiracal Formulas the simplest whole number ratios in a compound
Molecular formulas show the actual atoms/ and ...(guys finish the sentence.. i can't read my writing)

FINDING EMPIRACAL FORMULAS:
A sample of an unknown compound is analyzed and found to contain 8.4g of 'C', 21g of 'H', and 5.1g of 'O'
Find the empiracal formula


Example: 0.888 grams of a compound made up of C2H7O
C, H, and O are found to contain 0.576g of C and 0.120g of H
a) Find the mass of oxygen
b) Find the empiracal formula

0.120g

+ 0.57g

-----------

.696

*.696

-.888

----------

.192-->oxygen

C=.192 x mol=0.48-->4

H=.120xmol=.12--->10

O= .192xmol=.012-->1

Homework: Worksheet questions # 22, 23, 24

NOVEMBER 10

In the beginning of class Mr. Doktor gave us the answers to the 10-2 worksheet # 1-30
But ofcourse right after that we got some notes on the board !

PERCENTAGE MASS OF ELEMENTS IN COMPOUNDS
Molar Mass: g/mol
Molar Volume: 1/mol

example: 0.0263 mol of gas occupies a volume of 482.0 mL
calculate the molar volume. Is this at STP?
Molar Volume=0.482L/0.0263 mol = 18.33 L/mol
--> Find the % carbon by mass in ethane (C2H6)
C2H6
2(12)+6(1)=30g/mol
%C 24g/mol /(over) 30g/mol x100= 80%
%H 6g/mol / (over) 30g/mol

--> Find the % mass of each element in K2Cr2O7
2K= 78.2g/mol
2Cr= 104g/mol
70= 112g/mol/(over) 294.2g/mol
%K= 78.2g/mol /(over) 294.2g/mol =26.6% %Cr=104g/mol /(over)294.2g/mol =35.4%
%O= 112g/mol /(over)294.2g/mol =38.1%

FINDING MASS OF AN ELEMENT IN A GIVEN SAMPLE

example: Find the mass of carbon contained in a 25.0g sample of CO2

1C= 12g/mol %carbon= 12g/mol /(over) 44g/mol =27.3%
2O=32g/mol /(over) 44g/mol (o.273)(25.0g)=6.82g

32/44= (0.727)(25g)=18.12g
25g-6.82g=18.12g

Find the mass of Potassium, carbon and oxygen contained in 450.0 of K2CO3--138.2g/mol
K=254.7g K=56.6%
C=39.2g C=8.7%
O=156.2g O=34.7%

After taking notes Mr. Doktor gave us time to do our homework while checking around if we had completed the worksheet 10-2

Homework: worksheet # 20 & 21