Multistep Conversions

Multistep conversion take all the information mentioned in the previous molar-related posts and applies the processes to a question/exercise such as:

• 11.5g of H2 gas are placed in a balloon at STP. Determine the volume of the balloon? 

In such a scenario, one that you may encounter on any given day, you are being asked to convert between two units of factors with no direct relation (Mass cannot be converted in a single step into Volume; they represent separate measurements). Therefore, it is necessary to follow this convenient "road map": 

 

This is simplified by the following points: 

• Mass to Moles, and vice versa, uses Molar Mass - Atomic Mass of Element or Compound g/mol 
• Volume (at STP) to Moles, and vice versa, uses Molar Volume - 22.4 L/mol   
• Particles (Molecules/Atoms) to Moles, and vice versa, uses Avogadro's Number - 6.02 x 10^3   

Using such information, one can solve the aforementioned problem as follows: 

11.5 g (always begin with the given number) x 1 mole/ 2 grams = 5.75 moles 

5.75 moles x 22.4 Liters/ 1 mole = 129 Liters 

It is important that all the data and units are inserted and cancelled properly and for that, here's another "road map". 

  

And here is another example: 

• A sample of oxygen gas contains 3.5 x 10^21 molecules. How many grams of oxygen is this?

              3.5 x 10^21 molecules x 1 mole/ 6.02 x 10^23 molecules 

           =5.8 x 10^-3 moles 

             5.8 x 10^-3 moles x 2 (16.0) g */ 1 mole

           =0.19 grams of oxygen gas 

*Pay attention to isolating diatomic elements as their atomic mass becomes that of two molecules of that element*

The universality of the application of multi-step conversions, in that it is common in dimensional analysis and recurring in chemistry, is made even simpler by this video: 

-Simon Sierra

Iron & Copper Reaction Lab

This lab really tested not only our skills in chemistry, but also our skills in patience. It was time consuming but allowed us to see how quickly rust can form, although that was not the objective; the lab was designed so that we can use different conversion factors and data of varying data to analyze the chemical reaction of iron and copper. Iron Man approves! Better yet, Captain Kirk does!

He's eighty.  This is him at thirty-two:

Like a fine wine.

-George Spencer

Molar Volume Lab

This class was spent doing a lab to measure the molar volume of a gas. By filling a immersed cylinder with butane gas through the means of a lighter, we could interpret the volume of both cylinder filled and lighter emptied.

-Simon Sierra

Converting Between Volume and Moles

How Does One Convert Between Moles and Volume?

To convert between moles and mass, molar volume is utilized as the conversion factor. This introduces a new concept that is easily associated with our previous knowledge of the mole through the diagram below: 

What is Molar Volume?

At standard temperature and pressure (STP) one mole of any gas occupies the same volume. STP is found at 0 °C or 101.325 kPa, and at these levels 1 mole = 22.4 L. Therefore, 22.4 L/mole is the molar volume at STP.

With this conversion factor:

• You can convert from volume to moles
• You can convert from moles to volume 

What's the Process?

Like molar mass conversions, only one mathematical step is needed in these conversions: 

Examples 

• At STP an unknown gas is found to occupy 150 mL. How many moles of gas must there be? 

                         150 mL x 1 mole/ 22.4 Liters

                      = 6.70 milli-moles/ 1 000 

                      = 0.00670 moles  

• At STP, a sample of oxygen gas contains 11.5 moles. How many litters of oxygen gas are there?  

                      11.5 moles x 22.4 Liters/ 1 mole

                   = 258 L  

Below is a video that thoroughly goes over the process of converting moles to volume and back again:

  

-George Spencer

Converting Between Mass and Moles

How Does One Convert Between Moles and Mass?
To convert between moles and mass, molar mass is utilized as the conversion factor. Although simple it is important to that note that:

• The appropriate units are cancelled 
• The number of significant digits matches that of the least number of the given data  

What's the Process?

Only one mathematical step is needed in these conversions: 

 

Examples 

• How many moles are present in a 2.5 gram sample of Ammonium Phosphate?  
• Ammonium Phosphate = (NH3)PO4 
• (NH3)PO4 = 149 grams  

                         2.5 grams x 1 mole/ 149 grams 

                      = 0.017 moles 

• A sample of Hydrochloric acid contains 0.54 moles. How many grams of Hydrochloric Acid is this?  
• Hydrochloric Acid = HCl 
• HCL = 36.5 grams  

                        0.54 moles x 36.5 grams/ 1 mole 

                      = 20 grams

Below is a video that thoroughly goes over the process of converting moles to grams:

 

And likewise, here is one that explains how to convert from grams to moles: 

  

-Benedict Suratos

Molar Mass

What is Molar Mass? 

Molar mass is the mass (in grams) of 1 mole of a substance. 

How do you find Molar Mass? 

This number can be determined from the atomic mass given on the periodic table as shown below:

 

As you can see, there a0re four significant digits given in the atomic mass and in some instances even more. For our application and purposes, we will only use one digit past the decimal point for the atomic mass. Molar mass is expressed as g/mol, therefore the element above can be said to have a molar mass of 58.93 g/mol.  

• Hydrogen = 1.0 g/mol  
• Zinc = 65.4 g/mol 

How do you find Molar Mass of Compounds? 

To determine the molar mass of compounds, simply add the mass of all the atoms together: 

• Water (H2O) = 2(1.0) + 16.0 = 18.0 g/mol  
• Aluminum Chloride (AlCl3) = 27.0 + 3(35.0) = 133.5 g/mol  

The following video should clarify any confusions. Underneath that thick southern accent are some fine examples:

-Simon Sierra

Avogrado's Number

Avogadro's Number:

• Amedeo Avogadro proposed that the number of atoms in 12g of carbon be equal to a constant (This equals 1 mol of Carbon)
• This value is now called Avogadro's Number and forms the basis of all quantitive  chemistry
• Avogrado's Number: 6.02 x ×10
• For future conversions we can say and apply that: 1.0 Mole = 6.02 x 10 Atoms    
• Here's the fancy gentleman himself:   

 

He looks like a less refined Peter Lorre.   

- George Spencer

Hydrate Lab

On Friday, we did a lab on hydrates and it taught us how each hydrate has a specific amount of water that can be burned away and then measured.

-Ben Suratos

Classification and Nomenclature

Chemical Nomenclature:

The most common system is the IUPAC (International Union of Pure and Applied Chemistry) and is is used to name:

• Ions 
• Ionic Compounds   
• Multivalent Ions 
• Hydrates 
• Molecular Compounds 
• Acids and Bases 

Chemical Names and Formulas for Ions: 

An ion is an atom or molecular that is electrically charged due to the loss or gain of one or more electrons. 

• The chemical formula for an ion is represented with the symbol of the element and a superscript denoting the ion charge: Zn^2+  or  Se^2-   
• The name for an ion depends on whether it is a metallic or non-metal ion. 
• For metallic ions: the metal's name + ion = Zinc Ions 
• For non-metallic ions: the non-metal's name + "ide" + ion = Selenide Ion  

Chemical Names and Formulas for Ionic Compounds: 

An ionic compound is a bond between a positively charged molecule (cation) and a negatively charged molecule (anion)

• The chemical formula for an ionic compound is represented with the symbol of the positive element first and then the negative element. Superscripts are used to denote the ratio of charges, neutralizing the compound: BaCl2
• The name for an ionic compound uses the same order as the chemical formula without the subscripts and an "ide" for the anion: BaCl2 = Barium Chloride or SrF2 = Strontium Fluoride

Chemical Names and Formulas for Multivalent Ions: 

An multivalent ion are any atoms or molecules that have more than one common charge. The top number listed on the periodic table is the more common charge. While the chemical formula of these ions is similar to those of ionic compounds, the naming is fairly different. To name multivalent ions, there are two systems:

• The IUPAC System uses roman numerals in parenthesis to show the charge: Iron (III) Oxide
• The Classical System uses the latin names of these multivalent elements and 
• the suffix "-ic" for the larger charge: Ferric Oxide (Fe2O3) 
• the suffix "ous" for the smaller charge: Ferrous Oxide (FeO)   
• These classical names include 
• Ferr - Iron (Fe) 
• Cupp - Copper (Cu)
• Mercur - Mercury (Hg)
• Stann - Tin (Sn)
• Aunn - Gold (Au)
• Plumb - Lead (Pb) 
• Wolf - Tungsten (W)  
• Argent - Silver (Ag)   

Chemical Names and Formulas for Hydrates:  

Hydrates are substances chemically combined with water in a definite ratio.  

• The chemical formula for a hydrate takes another chemical formula and attaches the ratio of hydrate to H2O : Chemical Formula x # of Water Molecules+ H2O
• Cu(SO4) x 5H2O
• The name for a hydrate takes the name of another chemical formula and attaches the ratio of hydrates (number of water molecules) to it: Chemical Formula + Prefix (Mono-, Di-, Tri-, Tetra-...)+ "hydrate." 
• Copper (II) Sulphate Pentahydrate   

Chemical Names and Formulas for Molecular Compounds:  

Molecular compounds are any compounds made of two or more anions. It is important to note that some of these anions are diatomic or polyatomic in a solitary state: 

• H2 (Hydrogen)
• O2 (Oxygen)
• F2 (Fluoride)
• Br2 (Bromide)
• I2 (Iodine)
• N2 (Nitrogen)
• Cl2 (Chlorine)

• S8 (Sulphur)
• P4  (Phosphorus)

• The chemical formula is identical to that of an ionic compound
• The name for a molecular compound uses prefixes to denote the ratio of molecules in the compound: 
• Uses the name of the first element (usually no prefix)
• The name of the second element (w/ a prefix) and ends in "-ide"
• NO = Nitrogen Monoxide 
• Hydrogen does not get a prefix 
• H2S = Hydrogen Sulphide  

Examples include: 

• N2O4 = Dinitrogen Tetraoxide 
• CS2 = Carbon Disulphide 
• P4O10 = Tetraphosphorus Decaoxide  

Prefixes to know include:  

• Mono - 1
• Di - 2
• Tri - 3
• Tetra - 4 
• Penta - 5 
• Hexa - 6
• Hepta - 7
• Octa - 8
• Nona - 9
• Deca - 10 

Important Names and Formulas of Molecular Compounds: 

• Water - H2O 
• Hydrogen Peroxide - H2O2  
• Ammonia - NH3 
• Glucose - C6H12O6   
• Sucrose - C12H22O11  
• Methane - CH4 
• Propane - C3H8 
• Octane - C8H18 
• Methanol - CH3OH  
• Ethanol - C2H5OH   

Chemical Names and Formulas for Acids and Bases:  

For acids, hydrogen is always present in the compound. It appears first in the chemical formal unless it is part of a polyatomic group. To name acids, two systems are used: 

• The IUPAC System uses the aqueous hydrogen compound: HCl(aq)  = Aqueous Hydrogen Chloride    
• The Classical System uses the suffix "-ic" and or the prefix "hydro-": Hydrochloric Acid  

For bases, hydroxide is present in the compound, typically following the cation: NaOH or Ba(OH)2 

The same rule applies for naming: Sodium Hydroxide or Barium Hydroxide

Important Names and Formulas of Molecular Compounds:  

• Hydrochloric Acid - HCl 
• Nitric Acid - HNO3 
• Sulphuric Acid - H2SO4 
• Phosphoric Acid - H3PO4 
• Acetic Acid - CH3COOH 
• Ammonia - NH3  

-Simon Sierra

Electron Dot Diagrams

Drawing Electron Dot Diagrams

• The Nucleus is represented by the atomic symbol
• For individual elements determine the number of valence electrons
• Electrons are represented by dots around the symbol
• Four orbitals (one of each side of the nucleus) each holding a max of 2e
• each orbital gets 1e before they pair up

Examples of Lewis Dot Diagrams

      Lithium 

          Sulphur

Lewis Diagrams for Compounds & Ions

• In the covalent compunds electrons are shared

      1.) Determine the number of valence electrons for each atom in the molecule

      2.) Place atoms so that valence electrons are shared to fill each orbital

Example for Lewis Diagrams for Compounds & Ions

       Nitrogen Trichloride

Ionic Compounds

• In ionic compounds electrons transfer from one element to another
• Determine the number of valence electrons in the cation. Move these to the anion
• Draw [] around the metal and non-metal
• Write the charges outside the brackets

Examples of Ionic Compounds

         Sodium Chloride

-George Spencer

Period Tables and Trends

• Elements close together on the periodic table display similar characteristics.
• There are 7 important periodic trends.

1. Reactivity
2. Ion charge
3. Melting point
4. Atomic radius
5. Ionization energy
6. Electronegativity
7. Density*

Reactivity


-Metals and non-metals show different trends.
-The most reactive metal is Francium and the most non reactive element is Flourine.



Ion Charge

-Elements ion charges depend on their group(columns)






Melting points

-Elements in the center of the table have the highest melting point.
-Noble gases have the lowest melting point; starting from left to right melting point increases. (until middle of the table.



Atomic Radius
-Atomic radius decreases to the up and the right.
-Helium has the smallest atomic radius.
-Francium has the largest atomic radius.



Ionization energy
- The energy needed to completely remove aan electron from and atom.
- It increases going up and to the right.
- All Noble gases have high ionization energy.
- Helium has the highest ionization energy.
- Francium has the lowest ionization energy.
- Opposite trend of Atomic Radius.



Electronegativity

- Electronegativity is how much atoms want to gain electrons.
- Same trend as ionization energy.



- Ben Suratos