Define (n+l) rule with example.
1. Define bomb calorie meter with example.
Answers
According to (n+l) rule: Orbital which has the least value of (n+l) will be filled first to the electrons.
Example: 3s orbital will be filled first and then 3p orbital.
Orbital n l (n+l)
3s 3 0 3+0=3
3p 3 1 3+1=4
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A bomb calorimeter is a constant volume calorimeter (constant volume is isochoric). So the heat measured by such an instrument is equivalent to the change in internal energy or ΔU. The heat can be determined from the temperature change, ΔT, and the heat capacity of the calorimeter, Ccal. For a bomb calorimeter, the heat capacity is usually quite large due to all the water and the hardware (stirring paddles, blades, the stainless steel "bomb" holding the reactants, the wiring, the walls of the calorimeter, etc...). This value is Ccal. It is used to find qv of the system:
qcal=CcalΔT=−qv,system
Sometimes, it is more convenient to split the overall heat capacity of the calorimeter into its component parts: (1) the water, and (2) the hardware.
Ccal=Chardware+mwaterCs,water
The hardware heat capacity will be in units of J/K or kJ/K while the water heat capacity has to be calculated from the mass of the water and the specific heat of water (4.184 J g-1 K-1). So the water part is slightly variable due to the fact that you can fill the calorimeter up with slightly different masses of water each time you use it. If you put all that into one formula for a bomb calorimeter, you get:
qcal=ChardwareΔT+mwaterCs,waterΔT
One last thing to note. Many tables will list heat capacities using °C instead of K. Realize that these two units are equivalent in this context because we are using ΔT and not plain T. A change in Kelvin of 10 is exactly a change of 10 in °C as well. So don't try to change Celsius to Kelvin and vice versa here. This will be true throughout all your science courses.
Converting ΔU to ΔH
Chemists are almost always interested in the enthalpy change to know what would have happened at constant pressure. It is possible to get ΔH from a bomb calorimeter experiment. It just takes an additional step to do a conversion from ΔU to ΔH.
To convert from ΔU to ΔH requires knowing the amount of work done (w) during the reaction. In the case of a chemical reaction, work can be easily calculated by simply counting the number of moles of gas products and gas reactants.
Δngases=Σngasproducts−Σngasreactants
Now the work can be calculated with the formula:
work:w=−ΔngasesRT
So this leads to the final formula for the conversion:
ΔU=ΔH−ΔngasesRT
or with a little algebraic rearranging...
ΔH=ΔU+ΔngasesRT