Lab 3B & Naming Non-Acids and Acids

Today, we did a lab on separating mixtures on chromatography strips. The purpose of this lab was to calculate the Rf (ratio of fronts) values and identify each component. This is to help us identify components of a mixture based on their invidivual Rf values.

Well, how do you calculate the Rf value?


Rf: d1 / 21
d1: distance traveled by solute
d2: distance traveled by solvent

eg. Solute traveled 9.0 cm and solvent traveled 12.0 cm. Find the Rf value.
Rf = 9.0/12.0
    =  0.75 cm

Based on this, we identified the Rf values of three primary food colorings: red, yellow and blue.
There were two mixtures, one green and the other was unknown. We could identify the different components based on observing the chromatography strips. The green food coloring was composed of yellow and blue, while the unknown was composed of all three primary colors. We confirmed it by comparing the Rf values and the average Rf values of the components. :)




Now, I will go over how to name non-acids & acids!


Naming Non-Acids


IONIC COMPOUNDS

• composed of a metal (positive ion) and a non-metal (negative ion)
• when naming ionic compounds, make sure the ions always equal to zero
• change the ending of the non-metal with the suffix "ide" unless it is a polyatomic atom (keep it as it is)
• some metals form more than one ion, so indicate the charge using Roman Numerals
  
  eg. CaCl2 > Calcium Chloride
        MnO2 >  Manganese (IV) Oxide
        Pb(NO3)2 > Lead (II) Nitrate

COVALENT COMPOUNDS

• non-metal + non-metal
• make sure the ions equal to zero
• use Greek prefixes to identify if there is more than one atom
• do not use "mono" for the first element
• the last non-metal should end in "ide"
  
  Greek Prefix                Corresponding Number
  mono                                         1
  di                                              2
  tri                                              3
  tetra                                          4
  penta                                         5
  hexa                                          6
  hepta                                         7
  octa                                           8
  nona                                           9
  deca                                          10
  
  
  eg. SF3 > Sulphur Trifluoride
        H2S > Dihydrogen Monosulphide

Naming Simple Acids (Hydrogen + Another Element)

• use the prefix "hydro"
• drop the "ide" on the non-metal element and end with the suffix "ic"
• add the word "acid" at the end
  
  eg. hydrogen chloride >> hydrochloric acid

Naming Complex Acids (Hydrogen Ion + Polyatomic Ion)

• drop the "hydrogen"
• if the polyatomic ion ends with "ate" replace it with "ic"
• if the polyatomic ion ends with "ite" repliace it with "ous"
• add "acid" at the end
  
  eg. hydrogen chlorate >> chloric acid
       hydrogen hypochlorite >> chlorous acid

Good news for you, there is an easy way to remember the rules!
* We ate-ic-y sushi and got appendic-ite-ous   :)

Law of Definite Composition (Proust's Law)

• a chemical compound always contains exactly the same proportion of elements by mass (so nothing will be left over)
  
  eg. H2O (water) has two atoms of hydrogen (2g) and one atom of oxygen (16g)
  Total mass: 18g

Law of Multiple Proportion (Dalton's Law)

• same elements can combine in more than one proportion to form different compounds
• one element with the same mass combine with the different masses of another element are in the ratio of small whole numbers
  
  eg. CO (one oxide) and CO2 (two times the number of oxide)
  or FeO and Fe2O3

entry by grace