Midterm 1 Practice Problems.pdf

# 8 you are given an unknown substance with the

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8. You are given an unknown substance with the following composition: C = 74.03% H = 8.698% N = 17.27% What is the empirical formula for the substance? 9. If the compound in number 8, above, has a molecular mass of 162.24 g/mol, what is the molecular formula for the compound?

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10. One granule of sucrose (C 12 H 22 O 11 ) weighs 2.5 micrograms. How many sucrose molecules are in that granule? 11. Consider five solutions that all have the same mass of solute in 100.0 mL of solution. Which has the highest concentration as measured in molarity? A. KCl B. NaCl C. Na 2 SO 4 D. NaF E. CaCl 2 For questions 12-14, use the following information: A common rocket fuel, dimethyl hydrazine (C 2 H 8 N 2 , MM = 60.106 g/mol), reacts with dinitrogen tetroxide (MM = 92.02 g/mol) to produce nitrogen gas, carbon dioxide, and steam: ___ C 2 H 8 N 2 (l) + _ _ _ N 2 O 4 (g) _ _ _ N 2 (g) + _ _ _ CO 2 (g) + _ _ _ H 2 O (g) This is an UNBALANCED equation BALANCE FIRST !! 12. What mass of water vapor is produced when 50.0 g of C 2 H 8 N 2 reacts with 150.0 g of N 2 O 4 ? 13. Calculate the mass of the reactant in excess that remains after the reaction. 14. Calculate the percent yield if 52.1 g of steam are actually produced.
Potentially helpful information Conversion factors : Length 1 m = 1.094 yd 1 mi = 5280 ft

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