<span>J.j thomson a british physicist was the first to identify the electron in 1987</span>
Answer:

Explanation:
The Rydberg equation gives the wavelength λ for the transitions:

where
R= the Rydberg constant (1.0974 ×10⁷ m⁻¹) and

Data:

λ = 657 nm
Calculation:

Answer:
Petrochemicals are chemical products derived from petroleum, although many of the same chemical compounds are also obtained from other fossil fuels such as coal and natural gas or from renewable sources such as corn, sugar cane, and other types of biomass.
Answer : The energy required to melt 58.3 g of solid n-butane is, 4.66 kJ
Explanation :
First we have to calculate the moles of n-butane.

Given:
Molar mass of n-butane = 58.12 g/mole
Mass of n-butane = 58.3 g
Now put all the given values in the above expression, we get:

Now we have to calculate the energy required.

where,
Q = energy required
= enthalpy of fusion of solid n-butane = 4.66 kJ/mol
n = moles = 1.00 mol
Now put all the given values in the above expression, we get:

Thus, the energy required to melt 58.3 g of solid n-butane is, 4.66 kJ