A first-order decay process for a radioactive isotope is shown below. Which figure shows the composition at 12 years?     

Which balanced thermochemical equation corresponds to the enthalpy of formation (ΔHfo) of carbon monoxide, CO(g)? The enthalpy of formation (ΔHfo) of CO(g) is –110.53 kJ/mol 

What mass of sodium hydroxide (NaOH, molar mass = 40.0 g/mol) is needed to make 100.0 mL of a 0.125 M NaOH solution?

A 1.0 L flask is filled with NO and O2 initially, and after the reaction establishes equilibrium, the flask is found to contain 0.0018 mol NO, 0.0012 mol O2 and 0.78 mol NO2. What is the value of the equilibrium constant, Kc, at this temperature? 2NO(g) + O2(g) ⇌ 2NO2(g)

What happens when the two solutions shown are combined? The Ksp of strontium sulfate, SrSO4, is 3.8×10–7.        

What is the molecular geometry around the indicated O atom in the molecule depicted?   

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)  

A 1.0 g sample of zinc sulfide, ZnS, is mixed with 100.0 mL of pure water and 100.0 mL of a 0.100 M sodium sulfide, Na2S, solution. Which set of diagrams best represents the two solutions? The Ksp of ZnS is 3.0×10–23, and both solutions are saturated. Water molecules and sodium ions are omitted for clarity.

What is the correct formula for iron (III) sulfide?

The reaction of: NO(g) + Cl2(g) ⇌ NOCl(g) + Cl(g) Is found to have an equilibrium constant of 1.1×108 at a particular temperature. What does this mean?