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A balloon contains 0.86 mol N2, 0.22 mol O2, 0.061 mol He and 0.049 mol H2. Calculate the mole fraction of O2.   

Calculate the wavelength (in meters) of a radiation that has a frequency of 1.25 × 1014 Hz.

Of the four atoms, Ge, Ca, S, Si ____ is the most electronegative.

The 227Ra2+ ion  [Z = 88] contains how many neutrons (n) and electrons (e)?

Which is expected to have the highest surface tension at 25 °C?

The density of potassium is 0.86 g/cm3 (or 0.86 g/mL). What is the volume, in mL of 0.50 kg of potassium (pay attention to kg vs. g)?

The number of lone pairs of electrons around the central atom in SbCl3 is:

The phosphorus atom in PCl3 would be expected to have a ______________.

Air flowing at 370 kg/s enters a turbine at 1580 K, 13 bar and leaves at 1 bar. The turbine operates with an isentropic efficiency of 85%.   Assume variable specific heats. Determine the work generated by the turbine (MW).

What is the method of each of these disciplines?