A source contains two phosphorous radio nuclides `""_(15)^(32)P(T_(1//2)=14.3d) and ""_(15)^(33)P(T_(1//2)=25.3d)` Initially, 10% of the decays come from 33 15P. How long one must wait until 90% do so?

If the lines (2x-1)/(2) = (3-y)/(1) = (z-1)/(3) and (x+3) /(2) = (z+1)/(p) = (y+2)/(5) are perpendicular to each other, then p is equal to a) 1 b) -1 c) 10 d) - (7)/(5)

The radio isotope ""_(15)^(32)P is used to bio-chemical studies. A sample containing this isotope has an activity 1000 times the detectable limit. How long could an experiment be run with the sample before the radioactivity could no longer be detected ? Half-life of ""_(15)^(32)P is 14.2 days.

For an ideal gas, an illustration of three different paths A, (B +C) and (D+E) from an initial state P _(1) , V _(1), T _(1) to a final state P _(2), V _(2), T _(1) is shown in the given Path A represents a reversible isothermal expansion from P _(1), V _(1), to P _(2), V _(2) Path (B +C) represents a reversible adiabatic expansion (B) from P _(1), V _(1), T _(1) to P _(3), V _(2) , T _(2) followed by reversible heating the gas at constant volume (C) from P _(3), V _(2), T _(2) to P _(2), V _(2), T _(1). Path (D+E) represents a reversible expansion at constant pressure P _(1) from P _(1) , V _(1), T _(1) to P _(1), V _(2), T _(3) followed by a reversible cooling at constant volume V _(2) (E) frm V _(1) , V _(2) T _(3) to P _(2) , V _(2), T _(1). What is Delta S for path A ?

For an ideal gas, an illustration of three different paths A, (B +C) and (D+E) from an initial state P _(1) , V _(1), T _(1) to a final state P _(2), V _(2), T _(1) is shown in the given Path A represents a reversible isothermal expansion from P _(1), V _(1), to P _(2), V _(2) Path (B +C) represents a reversible adiabatic expansion (B) from P _(1), V _(1), T _(1) to P _(3), V _(2) , T _(2) followed by reversible heating the gas at constant volume (C) from P _(3), V _(2), T _(2) to P _(2), V _(2), T _(1). Path (D+E) represents a reversible expansion at constant pressure P _(1) from P _(1) , V _(1), T _(1) to P _(1), V _(2), T _(3) followed by a reversible cooling at constant volume V _(2) (E) frm V _(1) , V _(2) T _(3) to P _(2) , V _(2), T _(1). What is q _(rav), for path (A) ?