Calculate the energy change when an electron moves from n=5 to n=7. Explain/show work please.

E = 1.55 ⋅ 10 − 19 J

Explanation:  

The energy transition will be equal to  1.55 ⋅ 10 − 1 J .  

So, you know your energy levels to be n = 5 and n = 3. Rydberg's equation will allow you calculate the wavelength of the photon emitted by the electron during this transition

1 λ  = R ⋅ ( 1 n 2 final  − 1 n 2 initial  ) , where λ - the wavelength of the emitted photon; R

- Rydberg's constant -  1.0974 ⋅ 10 7 m − 1 ; n final - the final energy level - in your case equal to 3; n initial - the initial energy level - in your case equal to 5. So, you've got all you need to solve for  λ , so 1 λ  =

1.0974 ⋅10  7 m − 1 ⋅ (     −152    

)

1

λ

=

0.07804

⋅

10

7

m

−

1

⇒

λ

=

1.28

⋅

10

−

6

m

Since  

E

=

h

c

λ

, to calculate for the energy of this transition you'll have to multiply Rydberg's equation by  

h

⋅

c

, where

h

- Planck's constant -  

6.626

⋅

10

−

34

J

⋅

s

c

- the speed of light -  

299,792,458 m/s

So, the transition energy for your particular transition (which is part of the Paschen Series) is  

E

=

6.626

⋅

10

−

34

J

⋅

s

⋅

299,792,458

m/s

1.28

⋅

10

−

6

m

E

=

1.55

⋅

10

−

19

J

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.