Ch.3 - Chemical ReactionsWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Solution: Vitamin A has a molar mass of 286.4 g/mol and a general molecular formula of C xHyE, where E is an unknown element. If vitamin A is 83.86% C and 10.56% H by mass, what is the molecular formula of vita

Solution: Vitamin A has a molar mass of 286.4 g/mol and a general molecular formula of C xHyE, where E is an unknown element. If vitamin A is 83.86% C and 10.56% H by mass, what is the molecular formula of vita

Problem

Vitamin A has a molar mass of 286.4 g/mol and a general molecular formula of C xHyE, where E is an unknown element. If vitamin A is 83.86% C and 10.56% H by mass, what is the molecular formula of vitamin A?

Solution

Recall that the molecular formula of a compound is the actual molar ratio (ratio of moles) for each element.  


For Vitamin A, the general molecular formula is given as: CxHyE, where E is an unknown element. Its molar mass is known to be: 286.4 g/mol, and it also contains 83.86% C, and 10.56% H by mass. We need to find the whole number values for x and y


To solve for the molecular formula of Vitamin A we need to do these steps: 

  1. Determine mass % of E 
  2. Based on the molar mass; determine the identity of element E
  3. Determine the # of moles of C and H and E using the mass from step 1.
  4. Get the whole number mole ratio of each element. 
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