1 / 8

Calculating Molecular Formula

Mole (mol) : The SI base unit that measures an amount of a substance; 1 mole of molecules has a mass equal to the molecular weight in grams. 1 mole = 6.02x10 23 atoms (molecules)

kylie-bird
Download Presentation

Calculating Molecular Formula

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Mole (mol): The SI base unit that measures an amount of a substance; 1 mole of molecules has a mass equal to the molecular weight in grams. • 1 mole = 6.02x1023 atoms (molecules) • When looking at a chemical reaction, the number of moles are indicated by the coefficients in front of the formula’s. • Avogadro’s Number: The number of molecules in one mole for any substance; 1mole of particles = 6.02 x 1023 2 moles of particles = 12.04 x 1023 3 moles of particles = 18.06 x 1023 etc . . .

  2. Calculating Molecular Formula • When supplied with the Empirical Formula, and the Molecular Mass, we are capable of calculating the Molecular Formula with the following equation: Mass MF Mass EF Example: The empirical formula is CH and the molecular mass is 26, what is the molecular formula?

  3. Gram Formula Mass (GFM) • The GFM is the total mass of any substance (element or compound) Example: K2CO3 (2 K atoms, 1 C atom, and 3 O atoms) Mass K = 39g Mass C = 12g Mass O = 16g (39x2) + (12x1) + (16x3) = 138 grams The gram formula mass of K2CO3 = 138g

  4. WHAT YOU KNOW!!!! GFM = 1 mole = 6.02 x 1023 molecules = 22.4 L • This is the most important information for you to memorize in order to master this unit. • The above means that the GFM of any substance (element or compound) is the same thing as saying 1 mole of that substance, which is the same as saying there are 6.02 x 1023 molecules of that substance, which is the same as saying there is 22.4 L of that same substance!!

  5. MoleMass / MassMole Converstions • Table T: mole = given mass GFM Example: If you have 54 grams of LiF, how many moles do you have? Example: If you have 2.3 moles of CuCl2, how many grams do you have?

  6. Stoichiometry Mole-Mole Problems: • Answers how many moles of one element or compounds react with a given number of moles of another element or compound. Example: How many moles of Ca are needed to react completely with 6 moles of H2O in the following reaction: Ca + 2H2O  Ca(OH)2 + H2 • Cross out anything in the equation that the problem is not considering. • Write the coefficient of each substance remaining under the element or compound. • On top of the element or compound write the number of moles given in the problem. • Set up a proportion:

  7. Percent Composition • The percentage by mass of each of the elements in compound • Table T: % composition = mass part x 100 mass whole Example: What is the percent by mass of magnesium in magnesium oxide (MgO)?

  8. Percent Composition • Hydrate: a compound that incorporates water molecules into its fundamental solid structure. The compound has a dot after it followed by the number of water molecules attached. • Ex: CaSO4•2H2O (SOLVE THE GFM) • The dot in the hydrate equates to an addition sign when calculating the GFM of a hydrate.

More Related