Why is heptane used as the blank? why did the spectrometer need to be recalibrated?

In any atom of any element, you will find protons and neutrons in the nucleus of any atom 

The answer you are looking for is option d

Answer:             1.0  × 10⁻⁵ msolution:                     as we know ph is given as,                                    ph  = -log [h⁺]and,                                    [h⁺]  =  10^-ph    (1)putting value of ph in eq. 1,                                    [h⁺]  =  10⁻⁵                                    [h⁺]  =  1.0  × 10⁻⁵ m

The answer is a its density hope i