Which of the following statements about semi-empirical methods are true: It can be used for static molecules but not for reactions in which bonds are forming or breaking. It combines a theoretically sound model of bonding with some experimentally determined parameters. It can determine precisely both the location and the energy of bonding electrons. It is good at predicting structural properties that arise from subtle interactions of orbitals.

The true statement about semi-empirical methods is:

It combines a theoretically sound model of bonding with some experimentally determined parameters.

Explanation:

Semi-empirical methods are theoretical assumptions combined with experimental data to improve computational performance.  In modern computational chemistry, semi-empirical methods play important roles. The methods offer the advantage of a substantial reduction in computational time.  They also increase one's ability to carry out calculations for large molecules.  However, with these methods, there is the added loss of the variational principle because one can obtain a total energy that is below the true total energy.  Again, semi-empirical methods have limited applicability because the methods apply to molecules with parameterized elements.  Semi-empirical methods may supply spurious results, especially since the molecular systems may be different from those used for parameterizations.

percent abundance for cu-63 can be shown as:

63 x + 65 (1-x) = 62.9296

65 - 62.9296 = 2 x

x = 1.035

thus, percent abundance for cu-63 is 1.035

percent abundance for cu-65 can be shown as:

63 x + 65 (1-x) = 64.9278

65 - 64.9278 = 2 x

x = 0.0361

thus, percent abundance for cu-63 is 0.0361

the mass spectrum of cu-63 showing the intense peak as, this isotope is found in nature more abundantly around 92.38 % in comparison to cu-65 which is found 62.58 % naturally