An unknown mass of Na2O (molar mass=61.979 g/mol) was dissolved in enough water to create a 150.0 mL stock solution. A 5.00 mL sample of the stock solution was transferred to a volumetric flask and diluted to 500.0 mL . The pH of the dilute solution is 13.23 1. Calculate the concentration of OH− ions in the dilute solution
2. Calculate the concentration of OH− ions in the stock solution
3. Determine the original mass of Na2O dissolved in the stock solution.

Two nitro no2 groups are chemically bonded to a patch of surface. they can't move to another location on the surface, but they can rotate (see sketch at right). it turns out that the amount of rotational kinetic energy each no2 group can have is required to be a multiple of ε, where =ε×1.010−24 j. in other words, each no2 group could have ε of rotational kinetic energy, or 2ε, or 3ε, and so forth — but it cannot have just any old amount of rotational kinetic energy. suppose the total rotational kinetic energy in this system is initially known to be 32ε. then, some heat is removed from the system, and the total rotational kinetic energy falls to 18ε. calculate the change in entropy. round your answer to 3 significant digits, and be sure it has the correct unit symbol.

What is i fracture in the crust called when land move up, down or sideways

Describe at least two advantages and two disadvantages of using hydropower as a source of energy.