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A 10 gram sample of which substance contains the greatest number of hydrogen atoms?   Data sheet and Periodic Table

What is the standard enthalpy change for the reaction?  2NH3(g)N2H4(l) + H2(g)N2H4(l) + O2(g)N2(g) + 2H2O(g)               ΔH°1 = –543 kJ·mol–12H2(g) + O2(g)2H2O(g)                              ΔH°2 = –484 kJ·mol–1N2(g) + 3H2(g)2NH3(g)                               ΔH°3= –92 kJ·mol–1   Data sheet and Periodic Table

In a 10.0 L vessel at 100.0 oC, 10.0 grams of an unknown gas exert a pressure of 1.13 atm.   What is the gas? Data sheet and Periodic Table

The molar enthalpy of formation for H2O(l) is –285.8 kJ·mol–1.  Which expression describes the enthalpy change for the reaction:2H2O(l)2H2(g) + O2(g)                ΔH° = ?  Data sheet and Periodic Table

Which gas, helium or argon, effuses faster under the same conditions and by how much? Data sheet and Periodic Table         

What is the mass (in g) of 0.935 mol of acetone, CH3COCH3?  The molar mass of acetone is 58.08 g∙mol–1.   Data sheet and Periodic Table

Strontium (Sr, atomic number 38, average atomic mass = 87.62) naturally exists as 4 stable isotopes with masses of 84, 86, 87, and 88.  Which statement is correct?  Data sheet and Periodic Table

Which is the best Lewis structure for nitrogen monoxide?  Data sheet and Periodic Table

What is the formal charge on nitrogen in the nitrate ion?           Data sheet and Periodic Table

What is the atomic number of an ion with a –2 charge when it has 18 electrons?   Data sheet and Periodic Table