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Work hard. Be nice. Name: ____________________________________ KIPP NYC College Prep Period: ________ Date: ___________________ General Chemistry UNIT 7: Chemical Reactions Lesson 5: Empirical vs. Molecular formulas! By the end of today, you will have an answer to: What are empirical and molecular formulas? Do Now: Consider the following two compounds. NO2 and N2O4 Are these compounds ionic or covalent? Explain in-terms of electrons. NO2 N2O4 Name: Name: Draw a particle diagram of 2NO2 Draw a particle diagram of N2O4 Explain one similarity and one difference between 2NO2 and N2O4. Mini-Lesson: Empirical Formula: A compound whose elements are found in the simplest whole number ratio. Used in covalentlybonded molecules. Circle the compound that appears as an empirical formula: o NO2 or N2O4 Explain your reasoning: _____________________________________________________________________________________________________________________________ _____________________________________________________________________________________________________________________________ Circle the compound in the pair that is found in an empirical formula: CH2O or C3H6O3 P2O4 or PO2 C4H10O2N4 or C2H5ON2 Write the empirical formula for the following compounds: N2O6 ____________________________ P3O6 _____________________________ C11H22O11 __________________________ ***Ionic compounds are always found in an empirical formula. Example: NaCl vs. Na2Cl2 Work hard. Be nice. PRACTICE TIME! Directions: Determine the empirical formula for the following compounds. 1. C3O6 _____________________________________ 2. N3H9 _____________________________________ 3. C6H12O6 _____________________________________ 4. 5. What is the empirical formula of a compound that has a carbon-to-hydrogen ratio of 2 to 6? (1) CH3 (3) C3H (2) C2H6 (4) C6H2 6. The compounds C2H4 and C4H8 have the same (1) freezing point at standard pressure (2) boiling point at standard pressure (3) molecular formula (4) empirical formula 7. 8. Determine the empirical formula of C2H8N4O2. [1] ***Challenge: Sucrose, or table sugar is C12H22O11. Determine the empirical formula. Work hard. Be nice. Refresher: Types of Reactions! 9. In which type of reaction does a single reactant break down into two or more substances? (1) Synthesis (2) Decomposition (3) Single replacement (4) Double replacement 10. Which type of reaction does the following represent: Fe + 2 HCl FeCl2 + H2 (1) Synthesis (2) Decomposition (3) Single replacement (4) Double replacement Refresher: Law of Conservation of Mass! 11. In an experiment, 3.67 grams of lead completely reacts with oxygen, producing 5.25 grams of lead (II) oxide. Determine the total mass of oxygen consumed. 12. Which equation shows conservation of atoms? (1) 2N2 + O2 2N2O (2) 2N2 + 2O2 2N2O (3) N2 + O2 N2O (4) N2 + O2 2N2O 13. Given the balanced equation representing a reaction: CaCl2 (s) Ca (s) + Cl2 (g) What is the total mass of CaCl2 (s) that produces 60 grams of Ca(s) and 34 grams of Cl2(g)? (1) 36 g (3) 26 g (2) 60 g (4) 94 g More practice Balancing Equations! 14. ____ CaCl2 ____ Ca + ____ Cl2 15. ____ Sn + ____ Cl2 ____ SnCl4 Type of reaction: _____________________________________________ Type of reaction: _____________________________________________ 16. 17. ____ FeO ____ Fe + ____ O2 Type of reaction: _____________________________________________ ____ Fe + ____ HCl ____ FeCl2 + ____ H2 Type of reaction: _____________________________________________ 18. _______Ca(OH)2 + _______ NH4Cl _______NH4OH + _______ CaCl2 Type of reaction: _____________________________________________ 19. _______Pb(NO3)2 + _______NaI _______PbI2 + _______NaNO3 Type of reaction: _____________________________________________ Work hard. Be nice. ADDITIONAL PRACTICE: 5. ____ SnO2 + ____ C ____ Sn + ____ CO 6. ____ H2O ____ H2 + ____ O2 Type of reaction: _____________________________________________ Type of reaction: _____________________________________________ 7. ___ PbO + ____ H2S ____ PbS + ____ H2O 8. ____ N2 + ____ O2 ____ N2O5 Type of reaction: _____________________________________________ Type of reaction: _____________________________________________ 9. _____ K + _____CaO ________K2O + _______Ca 10. _______ SnO2 + _______H2 ________ Sn + _________ H2O Type of reaction: _____________________________________________ Type of reaction: _____________________________________________ Conclusion: 1) Why does the number of atoms have to be equal on both sides of the chemical equation? _____________________________________________________________________________________________________________________________ _____________________________________________________________________________________________________________________________ 2) Why can’t you change the number of atoms in an equation by modifying the subscript? _____________________________________________________________________________________________________________________________ _____________________________________________________________________________________________________________________________ 3) Explain the difference between 2CO2 and 1C2O4. Answer which one is empirical. _____________________________________________________________________________________________________________________________ _____________________________________________________________________________________________________________________________