# If an electron in H-atom has an energy of – 78.4 kcal/mol…

Problem : If an electron in H-atom has an energy of – 78.4 kcal/mol. The orbit in which the electron is present is:

(A) 1st

(B) 2nd

(C) 3rd

(D) 4th

Ans: (B)

Solution: $\large E_n = -\frac{313.6}{n^2} kcal/mol$

$\large – 78.4 = -\frac{313.6}{n^2}$

n = 2