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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

What is the final temperature when a 5.0 g sample of brass initially at 25 oC absorbs 75 J of heat?  The specific heat of brass is 0.38 J·g–1·°C–1. Data sheet and Periodic Table

What is the percent yield when 1.72 g of H2O2 decomposes and produces 375 mL of O2 gas measured at 42 oC and 1.52 atm?  The molar mass of H2O2 is 34.02 g∙mol–1.                2H2O2(aq)2H2O(l) + O2(g)   Data sheet and Periodic Table

The figure represents the initial contents of a reaction vessel mixture of nitrogen monoxide (NO) and oxygen (O2) at a pressure of 1 atm.  Keeping the volume and temperature constant, what are the final total pressure (Ptot) and partial pressure of nitrogen dioxide (PNO2) when the reaction is complete (assuming a 100% yield)?             2NO(g) + O2(g)2NO2(g)             Data sheet and Periodic Table

An enriched sample of carbon contains 20.0% 12C and 80.0% 13C.  Which figure shows this sample?Stem image:       Key:         Data sheet and Periodic Table

EXTRA CREDIT: The principle tissue found behind the retromammary space is 

The ratio of doses received with and without the wedge on the central axis at a point 10 cm beyond the depth of maximum dose in a phantom is called the