Atoms & Molecules- Oct. 30

On Friday we learned about Atoms & Molecules:



For mono atomic elements
a molecule = an element
Eg. Ne=Ne

Diatomic elements
Molecule, Element
Cl2, Cl

Molecules of compounds
H-O-H


Molecule
2 'H' atoms in 1 molecule
1 'O' atoms in 1 molecule


Example:
Write Ammonium Carbonate ---> (NH4)2 CO3
N: 2
H: 8
O: 3
C: 1

Moles <-----> Molecules
6.02 x 10^23 molec/ 1 mol


Example:
How many molecules are in 0.25 mol of CO2?
0.25 mol x 6.02 x 10^23/ 1 mol = 1.505 x 10^23 molec


Example:
5.1772 x 10^24 molecules of H2O = ? moles
5.1772 x 10^24 molecules 1 mol/6.02 x 10^23 =


Example:
Find the number of 'H' atoms in 4.0 mol of ammonia(NH3)?
moles--->molecules--->H atoms
4.0 mol x 6.02 x 10^23/ 1 mol = 2.41 x 10^24 molecules x 3 = 7.22 x 10^24 'H' atoms

Mole Ratio Lab - October 28 Class

Today in class, we completed the Mole Ratio Lab. Our objective of the lab was to find out the ratio of moles of iron, to moles of copper.

The Pre-Lab consisted of:
1) 2Fe + 3CuCl2 -> 3Cu 2FeCl3.
2) The ratio of moles of copper produced to moles of iron consumed is 3:2

The materials we used were:
Apparatus:
Beakers (250 mL)
Wash bottle
Stirring Rod
Crucible tongs
Centigram balance
drying oven
safety glasses
lab apron
plastic gloves
sand paper or emery cloth
face shield
Reagents:
copper (II) chloride
2 iron nails (approx. 5 cm)
1 M hydrochloric acid
distilled water

Our procedure:
1. Find the mass of 250mL beaker. Record the mass to the nearest hundredth of a decimal (g)
2. Add 8g of copper (II) chloride crystals to the beaker. Find and record the mass.
3. Add 50mL of distilled water to the beaker. To dissolve the crystals, swirl the beaker around.
4. Clean and dry 2 nails. Use sand paper if needed. Then, find and record the mass of the nails.
5. Put the nails into the solution and leave them there for 20 min. Observe the formation of copper and some of the iron that will be used up in the beaker.
6. Pick up the nails one by one using the tongs. Before removing the nails from the beaker, use distilled water to rinse off any remaining copper. Use a stirring rod to scrape any excess copper if needed. Let the nails dry on a paper towel.
7. Find and record the mass of the nails after they are completely dry.
8. (Decant- pour off only the liquid from a container that is holding both liquid and solid.)
Decant the liquid from the solid by putting the liquid into another beaker.
9. After decanting, rinse the solid with 25mL of distilled water. Decant again. Repeat this step 4 more times.
10. Wash the solid with 25mL of 1M hydrochloric acid. Decant again (twice). Then clean the solid with 25mL of distilled water.
11. Place the oven in a drying oven to dry.
12. Let the copper dry, then find and record the mass of the beaker + copper.
13. Make sure to clean up your lab and wash your hands properly.

Our observations:
Mass of empty dry beaker = 159.34g
Mass of beaker + copper (II) chloride = 167.34g
Mass of 2 iron nails = 5.45g
Mass of 2 iron nails (after) = 4.95g / 5.0g
Mass of beaker with copper (after) = 160.72g

We discovered that 0.5g of iron was used in the reaction and 4.95 g of copper was produced.
Our final ratio was 1.5:1 and we had a percent error of 56%. This is because we could have spilled some of the liquids and there was too much liquid in the copper and it didn't dry out fully.

Gases & Moles - Oct. 26 Class

Gases and Moles

The volume of a balloon occupied by a certain gas depends on the temperature and pressure.

Standard Pressure & Temperature (STP)

* 0°C & 101.3 kPa

(273 K)

Standard Ambient Temperature & Pressure (SATP) (24.8L/mol)
* 25°C & 100kPa

(298 K)

The volume of 1.0 mole of any gas at STP is 22.4

The molar volume at STP is 22.4L

Example

1) Find the volume occupied by 0.060 mol of CO2 gas at STP

2) Find the number of moles in a 264.0 mL sample of NO2 at 0° and 101.3 kPa(STP)

3) Find the volume occupied by 22.0g of CO2 (g) at STP

Atomic Mass - October 21st Class

Today, in class we learned how to find the molar mass in compounds.
Atomic Mass: The mass of 1 mole of atoms in an element
- The mass of 1.0 mol of 'C' atoms is 12.0g
- The mass of 1.0 mol of 'Ca' atoms is 40.1g

Molecular Mass: The mass of 1.0 mole of molecules of an element or compound
N2, O2, F2, Br2, H2, Cl2, I2
P4, S8

Assume all the rest are monoatomic



Finding the Molar Mass of Compounds
H2O
2 H= 2.0 (1.0) = 2.0
1 O = 1 (16.0) = 16.0
Total = 18.0 g/mol



- Find the molar mass of Ammonium phosphate

NH4+
PO4³- = (NH4)3PO4

3 N = 3(14.0) = 42

12 H = 12(1.0) = 12

1 P = 1(31.0) = 31

4 0 = 4(16.0) = 64

Total = 149 g/mol



Converting Mass <-> Moles

The Mole - Oct. 19 Class

In the beginning of class, Mr. Doktor showed us this really cool experiment involving this equation: 2 H2 + O2 -> 2 H2O

This is known as the Hydrogen bomb equation.





To count 1 mole, it will take:
6.03 x 10^23 = 1.0 x 10^22 mins
= 1.67 x 10^20 hours
= 6.97 x 10^18 days
= 2.3 x 10^17 months
= 1.94 x 10^16 years

The mole

1 mole = 602 000 000 000 000 000 000 000 = 6.02 x 10^23 -> Avogradro's number

2 H2 + O2 -> 2H20

2 H2 molecules + 1 O2 molecule -> 2 molecules of H2O

12.04 x 10^23 + 6.02 x 10^23 -> 12.04 x 10^23

of H2 molecules molecules of O2 molecules of water

How big is Avogadro's Number?

$1 mol

$6.02 x 10^23

6.0 x 10^9 = population of earth

$ 6.0 x 10^23

__________

6.0 x 10^9 ppl

= $1.0 x 10^14 -> $100 000 000 000 000

How gases combine

John Dalton

-look at masses of gases

11.1g of H2 reacts with 22.9g of O2

46.7g of N2 reacts with 53.3g of O2

42.9g of C reacts with 57.1g of O2

= No pattern

Joseph Gay Lussac

-combine gases based on volume

1L of H2 reacts with 1L of Cl2 -> 2L of HCl H2 + Cl -> 2 HCl

1L of N2 reacts with 3L of H2 -> 2L NH3

2L of CO reacts with 1L of O2 -> 2L CO2

= gases combine in simple whole number ratios

Avogadro's Hypothesis

-Equal volumes of any gas at a constant temperature and pressure contain equal numbers of molecules.

H2

same / but different mass

02

In conclusion, at the end of class, we did another really cool experiment known as the potato gun! It needs oxygen to react with chemicals.

Hydrate Lab

Today in class we learned tht hydrates are ionic compounds that contain an inorganic salt compound loosely bound to water. Putting our knowledge into action we did an experiment today that was meant to determine the emprical formula of a hydrate. In the lab we determined the anhydrous (without water) mass of the hydrate and then compared the original mass with the actual mass of water that should be present.

The materials that we used to conduct this experiment are:

- bunsen burner

- test tubes

- test tube rack

- test tube clamp

- weight scales

The first step we took in conducting our experiment is we filled a test tube with about 1 cm of the hydrate. We then carefully placed the test tube on the scale and recorded the mass of the hydrate and test tube. With extreme cation we proceeded to connect and light our Bunsen burner and adjusted the gas flow until the flame was about 5 cm tall. Afte heating our test tube over the Bunsen burner with the clamps (in and out) for about 5 minutes we carefully re-weighed the test tube.

Our observations were that the mass before heating was:

and the mass after heating was:

Our conclusion was that # amount of water was released during heating and that # percent of the hydrate was water. The actual percent ofwater in the hydrate was 45%. Our percent error was #.

Overall we learned a lot from the first-hand experience and had a great time!

Acids & Bases- Oct. 8 Class

In today's class we learned the characteristics of acids and bases.

Acids
- Solid, Liquid, or gas at SATP (25 degrees celcius, 100 kPa)
- Form conducting aqueous solutions
- Turn blue litmus red
- Dissolve in water to produce H+
- Taste sour


Bases
- Turn red litmus blue
- Slippery
- Non-conductive
- Dissolve in water to produce OH-




Naming Acids
- Acids are aqueous (dissolve in water)
- Hydrogen compounds are acids

• HCL(aq) --> Hydrochloric
• AcidH2SO4(aq) --> Sulfuric Acid
  

- Hydrogen appears first in the formula unless it is part of a polyatomic group

• CH3COOH(aq) --> Acetic Acid

- Classical rules use the suffix "ic" and/or the prefix "hydro"

• Eg. Hydrochloric Acid

- IUPAC system uses the aqueous hydrogen compound

• Eg. HCl(aq) --> Aqueous Hydrogen Chloride

Naming Bases
- For now, all bases will be aqueous solutions of ionic hydroxides

• NaOH
• Ba(OH)2
  

- Use the cation name followed by hydroxide

• Sodium Hydroxide
  
• Barium Hydroxide
  

Examples
- HI(aq) --> Hydrochloric Acid
- H3PO4(aq) --> Phosphoric Acid
- H3PO4(aq) --> Phosphorous Acid
- HNO3(aq) --> Nitric Acid
- HNO2(aq) --> Nitrous Acid
- Mg(OH)2 --> Magnesium Hyrdroxide
- HBr(aq) --> Hydrobromic Acid
- HOOCCOOH(aq) -- Oxalic Acid


How to make your own PH indicator between an acid and base!

October 6th 2009

Today in chemistry class Mr. Doktor showed us ...

Hydrates

- Some compounds can form lattices that bond to water molecules
Example: Copper Sulfate
- These crystals contain water inside them which can be released by heating
- Without water the compound is often preceded by “anhydrous”

Naming Hydrates

1. Write the name of the chemical formula.
2. Add a prefix indicating the number of water molecules.
3. Add hydrate after the prefix

Molecular Compound

- Composed of two or more non-metals.
- Low melting point and boiling point.
- Share (not exchange) electrons
- Usually end in –gen or –ine
Example: Hydrogen, Oxygen…
- 7 molecules are diatomic
They are… Hydrogen, Nitrogen, Oxygen, Fluorine, Cholrine, Bromine and Iodine
Two molecules are polyatomics.

Chemical Nomenclature - Oct 2 Class

In the beginning of class, Mr. Doktor showed us an example of electrolysis. He used pickles, water, and a battery charger. He then touched the pickle with the two wires, and you could see smoke come out and the pickle being electricuted. He then touched the water with the wires and smoke came out as well. You could see the hydrogen and oxygen as the smoke and you could smell this funky burning smell. You should not try this experiment at home due to dangerous results such as being electricuted or starting a fire.



Here is a video of an example of electrolysis.

http://www.youtube.com/watch?v=Or22ktW8btc&feature=related
This is a quick video that shows how hydrogen and oxygen atoms blow up a balloon. In my assumption, i believe that the balloon blew up due to evaporating water.



After that experiment in class, Mr. Doktor gave us examples and questions about naming compounds. Here are the examples done in class:
Name:
1. PbS2 - Lead (IV) Sulphide
2. MgO - Magnesium Oxide
3. CuCl2 - Copper (II) Chloride
4. Cr2O3 - Chromium (III) Oxide

Chemical Nomenclature
- Naming chemical compounds has been a very difficult task and different systems have been used through the centuries.
- Today the most common system is IUPAC for most chemicals.
- Ions
* Binary Ionic
- Polyatomic Ions
- Molecular Compounds
- Acids



Chemical Formulas
Be aware of the differences between ion and compound formulas.
Zn²+ - ion charge
BaCl2 - number of ions (Subscript)

Naming Ions
- For metals, use the name of the element and add ion
Eg. Al³+ = Aluminium Ion
- For non-metals, remove the original ending and add -ide
Eg. F- = Fluorine -> Fluoride

Polyatomic Ions have special names.

Binary Ionic
Steps:
1. Write the formula for the cation first and then the formula for the anion. (Cation = positive because "cat" = "pussytive" & Anion = Negative)
2. Criss cross charges moving the numbers below.
3. Reduce ion numbers to lowest common multiples, omit 1 and omit charges.
Eg.


Example
- Write the chemical formulas of:
Aluminum Fluoride = AlF3
Sodium Oxide = Na2O
Iron (III) Sulphide = Fe2S3

Multivalent Ions
- Some elements can form more than one Ion
Eg. Iron -> Fe³+ or Fe²+ / Copper -> Cu²+ or Cu¹+
- The more common ion is the top one of the P.T.
- IUPAC uses roman numerals in the parenthesis to show the charge.
- Classical (ie old) systems uses latin names of elements and the suffixes -ic (larger charge) and -ous (smaller charge)
FeO -> Ferrous Oxide
Fe2O3 -> Ferric Oxide

Other Classical Names
- Ferr = Iron
- Cupp = Copper
- Mercur = Mercury
- Stann = Tin
- Aunn = Gold
- Plumb = Lead
Chemical Formula: Sodium Nitrate -> NaNO3 (Na+/NO3-)
Barium Phosphate -> Ba3(PO4)2

Classification of Matter - September 30 Class

In this class, we learned about Homogeneous and Heterogeneous substances.. We distinguished that tap water is a heterogeneous substance because there are other chemicals that are put into the tap water when running through the drains, sinks, etc. Mr. Doktor also passed around a beaker filled with aluminum pieces and salt, a heterogeneous mixture that didn't react together. We also learned that there are certain ways of separating mixtures, which are mostly physical changes.

Notes:
Classification of Matter

• Understanding matter begins with how we name it. We can divide matter into two parts: Homogeneous substances and heterogeneous substances
  
• Homogeneous: consists of only one visible component
  - distilled water, oxygen, graphite
  
  
  
• Heterogeneous: contain more than one visible component
  - chocolate chip cookie, granite

Pure Substances:

• There are 2 types of Pure Substances:
  Element: substances that cannot be broken down into simple substances by chemical reactions
  - oxygen, iron, magnesium
• Compound: substances thar are made up of 2 or more elements & can change into elements (or other compounds by chemical reactions)
  - water, sugar

Telling the difference

• It is often very difficult to know if something is an element or a compound
  - The differences are only "visible" on the atomic level
• One method is to connect the substance to an electric current. This technique. called electrolysis can split the compound apart into its constituent compounds

Solution

• A solution is a homogeneous mixture of 2 or more substances
  - Solutions usually involve but don't have to (fog, steel)
• The compound present in greater mount is the solvent
  - Water is the most ommon solvent
  - The symbol (aq) is used when something is dissolved in water
• The compound present in smaller amount is the solute
  - In salt water, salt is the solvent

Mixtures

• Many mixtures are easy to identify (chocolate chip cookies) but others are easily confused as pure substances
• In heterogeneous mixtures.. the different parts are clearly visible (granite, sand)
• In homogenous mixtures.. the different parts are NOT visible (salt, water, air, brass)

Separating Mixtures

• There are many methods to separate mixtures, depending on how the type of mixture
  - By Hand (Heterogenous mixture only)
  - Filtration (Heterogeneous mixture only)
  - Distillation
  - Crystallization
  - Chromatography
• All of these are physical changes