1 / 11

Understanding Empirical Formulas: Solving Composition Problems Using Mole Concept

This guide explores empirical formula determination through a series of composition problems using the mole concept. We discuss compounds formed from elements like nitrogen (N), oxygen (O), carbon (C), and hydrogen (H) with various weight percentages. Through step-by-step explanations, we convert weights into formulas and derive empirical and molecular formulas. Additionally, practical combustion data is analyzed to assess hydrocarbon formulas. Get insights on how to approach empirical formula calculations in chemistry with real-world examples.

kacia
Download Presentation

Understanding Empirical Formulas: Solving Composition Problems Using Mole Concept

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. % composition problems: using mole concept to convert weights to formulas Sample % composition problem #1 A compound of N and O contains 63.63 wt % N and 36.36 wt % O. What is the empiric formula of the compound ?

  2. % composition Problem 1: empiric formula determination A compound of N and O contains 63.63% N and 36.36 %O. What is the empiric formula of the compound? let’s do it on the board…

  3. Sample problem #1; SUMMARIZED =Laughing gas OFFICIAL NAME… =>N2O Dinitrogen monoxide n nmin AW=Atomic wt (g/mol) n=w/AW moles w(g) 4.545 = 2 2.273 63.63/14= 4.545 63.63 14 36.36/16= 2.273 2.273 =1 2.273 36.36 16

  4. An oxide of nitrogen contains 46.7 wt. % N and 53.3 % O. What is it’s empiric formula ? (problem 35, page 417) • NO3 • NO2 • N2O • N3O7 • NO • None of the above

  5. % composition Problem 2: empiric formula determination with a twist A compound composed of C,H and O is 48.64% C and 8.16 % H and 43.2 % O by mass. What is the empiric formula ? Answer: C1.5H3O1 C3H6O2 x FACTOR 1.5*2= 3 48.64/12= 4.05 4.05/2.7= 1.5 ? 8.16/1= 8.16 3.0*2= 6 8.16/2.7= 3.0 43.2/16= 2.70 2.7/2.7= 1 1*2= 3

  6. A compound contains:0.3158 g C, 0.0526 g H and 0.631 g O. What is its empiric formula ? • C2H4O3 • C4H2O3 • CHO • CH2O • None of the above

  7. % composition Problem 3: empiric + molecular formula determination The previous empiric compound (C2H4O3) has a molecular weight of 228 g/mol. What is the molecular formula of the compound ? Let’s do this on the board…

  8. A compound with the empiric formula CH2O has a molecular weight of 180 g/mol. Given C=12 g/mol, H=1 g/mol and O=16 g/mol what is the molecular formula for the compound ? • CH2O • C3H6O3 • C6H12O6 • C12H24O12 • None of the above

  9. Chemical Compositions from Combustion Data 1) A 0.30 gram sample of carbon black is burned in a covered crucible. The collected gas weighs 0.70 grams. What is the empiric formula of the gas ? (C =12, O =16) ANSWER: CO

  10. Chemical Compositions from Combustion Data (continued) 2) A hydrocarbon sample (Cx Hy) is burned in oxygen producing 1.0 gram of CO2 and 0.4086 g H2O. What is the empiric formula for the hydrocarbon ? (C=12, O=16, H=1) ANSWER: CH2

  11. A similar text book problem to try: Page 418 Problem 51 Propane is a common hydrocarbon gas used for heating rural American homes. Complete combustion of a sample of propane produced 2.641 g CO2 and 1.442 g H2O. What is the empiric formula for propane ? (also called LNG=liquid natural gas) Answer: C3H8

More Related