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Friday, June 3, 2016

Simple Rules in Naming Chemical Compounds

A. Binary Compounds of Metal and Nonmetal
     This compound is composed of metal and nonmetal. If you want to learn how to name this compound just follow the simple rule below:

     Rule:  Name of metal  + Stem name of nonmetal + -ide ending
   
     Example:
          NaCl    =          Na           +        Cl
                       =      Sodium       +       Chlor (stem name of chlorine) +  ide
                       =      Sodium Chloride

     Some more examples:
         KCl       =   Potassium chloride
         MgO     =   Magnesium oxide
         Li2S      =   Lithium sulfide
         MgCl2  =   Magnesium chloride
         BeO     =   Berrylium oxide

B.  Binary Compounds of Nonmetal and Nonmetal
      This compound is composed of two nonmetals.  Now in naming this compounds prefixes are used.

 Prefixes

     1     -   mono
     2     -   di
     3     -   tri
     4     -   tetra
     5     -   pent
     6     -   hex
     7     -   hept
     8     -   oct
     9     -   nona
    10    -   dec

     Rule:  Prefix of first element except mono +  Name of first nonmetal + Prefix of second nonmetal + stem name of second nonmetal + ide

     Example: 

     CO =      C         +          O
           =    Carbon (1 carbon no prefix since mono)  +  Mono (1 oxygen ) + ox (stem name of oxygen) + ide 
           =    Carbon monoxide

     Other examples:
      
      CO2    -   Carbon dioxide
      NO3    -   Nitrogen trioxide
      N2O4  -   Dinitrogen tetraoxide
      CCl4   -   Carbon tetrachloride
      P2O4   -   Diphosphorus tetraoxide

C.  Binary Acids 
     This compound is composed of hydrogen bonded to a nonmetal

     Rule :  Hydro (constant prefix) + stem name of nonmetal + -ic acid

     Example :
 
    HCl   =          H          +         Cl
              =     Hydro   +   chlor  (stem name of chlorine) +  ic acid
              =    Hydrochloric acid

     Other examples;
     H2S    -   Hydrosulfuric acid  ( sulfur is exempted to the rule, full name is used)
     HF      -   Hydroflouric acid
     HBr    -   Hydrobromic acid


D.  Binary compounds of metal with variable oxidation number and nonmetal
      This compound is composed of metal having two or more oxidation number paired with a nonmetal.

     There are two rules to follow, one is by the use of IUPAC system of naming and the latin system of naming.

IUPAC System:

     Rule :  Name of metal + Roman Numeral showing the oxidation used in metal element +  Stem name of nonmetal  +  ide

     Example :

     FeCl2   =     Fe (+2 oxidation used)      +   Cl  (-1 oxidation used)
                 =     Iron (II) (II - indicates the oxidation number used of Fe)  +  Chlor (Stem name of chlorine + ide
                 =     Iron (II) chloride

     Other examples:

     FeCl3    -  Iron (III) chloride
     Fe2O3    -  Iron (III) oxide
     FeO      -  Iron (II) oxide

  Latin System:

     Rule :  Stem name of the latin name of metal ( but there are some exemption like Hg)  + ic ( is attached when the oxidation number used of the metal is higher) or  -ous (is attached when the oxidation number used of the metal is lower) + stem name of nonmetal + ide

     Example:

     FeCl2   =     Fe (+2 oxidation used)    +      Cl   (-1  oxidation used)
                  =    Ferr  ( Stem name of the latin name of Fe which is Ferrum)  +  ous ( ous is the suffix used for lower oxidation number  +  chlor (stem name of chlorine)  +  ide
                  =    Ferrous chloride
 
     Other examples:
   
     FeCl3     -   Ferric chloride
     Fe2O3     -   Ferric oxide
     FeO        -  Ferrous oxide

E.  Ternary Ionic Compounds
      This compound is composed of metal attached to a  polyatomic anion.

     Rule:   Name of metal ( use roman numeral of the oxidation number when metal has variable oxidation number +  name of the polyatomic anion.

     Example :

     NaOH   =     Na        +          OH
                  =    Sodium (the name of the metal)  + hydroxide ( name of the polyatomic anion)
                  =    Sodium hydroxide

     Other Examples:

     CaSO4        -  Calcium Sulfate
     Cu3PO4      -  Copper (I) phosphate
     Cu3(PO3)2 -  Copper (II)  phosphite


F. Ternary Acids (Oxyacids)
     Ternary acids are acids composed of hydrogen element paired to polyatomic anion.  This is also called oxyacids, acids containing oxygen.

     Rule :  Stem name of the element which is not hydrogen and oxygen (but there are some exemption, other element use full name like sulfur, carbon) + ous acid ( this is used when the ending of the polyatomic anion is ite) or ic acid (when the ending name of the polyatomic anion is ate).

     Example

     H2SO4   =       H      +    SO4  (sulfate, name of polyatomic anion)
                  =     Sulfur    +   ic acid ( ic acid is used because sulfate ends in ate)

     Other examples:

     H3PO3    -   Phosphorous acid
     H3PO4    -   Phosphoric acid
     H2SO3    -   Sulfurous acid


Try your knowledge by answering Pactice Test. Click  NAMING OF COMPOUNDS WORKSHEET













     
       
                   

Thursday, June 2, 2016

Concentration of Solution Sample Problems

A. Percent by Mass Sample Problems

     1.  What is percent by mass concentration of 12.5 g of NaCl dissolved in 200 g of water?

          Identify the given:   mass solute = 12.5 g NaCl
                                       mass solvent = 200 g water

          The problem is asking the percentage by mass of NaCl given the mass of solute and the mass of solution.  You have to take note that the mass of the solution is equal to the mass of solute + the mass of solvent.

          Formula:   

          Solution:
 

     2.   Calculate the percentage by mass of 30 g of KCl in 250 g of solution.

          Find the given:    mass of solute = 30 g KCl
                                    mass of solution = 250 g of solution

         Here the problem is asking to calculate the percentage by mass given the mass of the solute and the mass of the solution.

          Formula:

          Solution:

     3.  What is the mass of the CuSO4 present in 15% by mass 316 g of CuSO4 solution?
          
          Find the given:   Percent by mass = 15 %
                                   mass of solution =  316 g of solution

         The problem asked to calculate the mass of CuSO4, which is the solute of the solution.

          Formula : 
          Solution:
 


B. Percent by Volume Sample Problems

1.  A solution of hydrochloric acid is produced by dissolving 15 mL of HCl in enough water to make 240 mL of solution. What is the percentage composition of the solution?

     Find the given :    volume of solute = 15 mL
                                volume of solution = 240 mL

     This problem is asking the percentage  by volume of hydrochloric acid given the volume of solute and the volume of solution.

     Formula :

     Solution:
 

2.  Calculate the volume of alcohol present in 250 mL 70% alcohol solution and  40 % alcohol solution.

        Find the given:   volume of alcohol solution = 250 mL
                                 Percentage by Volume = 70 % and 40 %

        The problem is asking the volume of alcohol present in 70 % and 40% alcohol solution having 250 total volume of solution.  Two solutions are needed in this problem.

         Formula: 

          Solution:
     
          For 70% alcohol solution

          For 40% alcohol solution
 

     3. The average adult human body contains about 5 L of blood.  Only 0.72% consists of leukocytes (white blood cells).  What volume of leukocyte cells is present in the body of a small child, with only 2.5 L of blood?

         The given in this problem is the percent of white blood cells = 0.72% and the total volume of blood of a child blood = 2.5 L.

          The problem is asking to calculate the volume of leukocytes or the white blood cells.
         
         Formula:  

          Solution: 





C. Molarity Problems

1.  What is the molar concentration of the following solutions:
     a. 0.20 mol of NaCl in 0.25 L of solution.
     b.  5 g of sugar, C12H22O11 in 20 mL of solution.
     c.  3 g of KCl in 80 mL solution.

Formulas needed:


 Solutions:
     a.  Given :  mole solute = 0.20 mol
                      volume of solution = 0.25 L of solution


          Unit for Molarity can be mol/L or simply M.

     b.  Given:  mass of the substance = 5 g
                     volume of solution = 20 mL or 0.02 L
                     
           In this problem moles of solute should be calculated first, and needs the molar mass of sugar
    
           Molar mass of sugar = 12 (Atomic Mass of Carbon) + 22 (Atomic Mass of Hydrogen) + 11(Atomic Mass of Oxygen)

           Molar Mass of Sugar = 12(12) +22(1) + 11(16)
                                            =  144 + 22 + 176
                                            =  342 g/mol


           How to calculate mole of solute?


          Calculation of Molarity:

        


      c.  Given:  mass of the substance = 3 g of KCl 
                      volume of solution = 80 mL solution or 0.08 L 

          Molar mass of KCl = 1(atomic mass of K) + 1(Atomic Mass)
                                        =  1(39) + 1(35)
                                        =  39 + 35
                                        =  74 g/mol

         Calculation for mole of solute


         Calculation for molarity:

2.  What mass of solute is present in each of the following solutions?
      a.  400 mL of 0.05 M of  Calcium hydroxide, (Ca(OH)2) solution.
      b.  2.5 L of 1.00 M of sodium chloride, (NaCl) solution

       Solution:
      a.  Given :  Volume of solution = 400 mL or 0.4 L
                       molarity = 0.05 M or mol/L

          In this problem we need to calculate first the mole of the solute before we can calculate the mass.

        Calculating the moles of solute, formula is just rearrange:

   
         Calculating for the mass of solute, needs the molar mass of Ca(OH)2

          Molar Mass of Ca(OH)2 = 1(Atomic Mass Ca) + 2 (Atomic Mass O) + 2(atomic Mass H)
                                                 = 1(40g)  +  2(16g) + 2(1g)
                                                 =  40g + 32g + 2g
                                                  =  74 g/mol

           Calculating mass of the substance:

          

     b.  Given : volume of solution = 2.5 L
                      Molarity =  1 M of NaCl solution


         
            Before the mass can be calculated the mole of solute should be calculated first and the molar mass of the substance

            Molar Mass NaCl = 1 (23) + 1 (35)
                                         =  23 + 35
                                          =  58 g/mol

             Calculating the mole of solute:

                           

             Calculating mass of substance: