Phosphorous-32 undergoes beta decay. Formulate a balanced nuclear equation for this process.

The half-life of phosphorus-32 is 14.3 days. Calculate the mass, in g, of ³²P remaining after 57.2 days if the initial sample contains 2.63 × 10⁻⁸ mol. Use table 1 of the data booklet and M_r = 31.97 g mol⁻¹.

Explain the targeted alpha therapy (TAT) technique and why it is useful.

³²P → ³²S + \(_{-1}^0\)β 

Accept “e^–/e/β” instead of “\(_{-1}^0\)β”.

[1 mark]

ALTERNATIVE 1

«λ = \(\frac{{\ln 2}}{{14.3}}\) =» 0.04847 «day^–1»

«m(³²P) = 2.63 × 10^–8 mol × 31.97 g mol^–1 × e^{–0.04847 × 57.2} =» 5.26 × 10^–8 «g»

ALTERNATIVE 2

«\(\frac{{57.2}}{{14.3}}\) =» 4 «half-lives passed»

OR

«n(³²P) = \(\frac{{2.63 \times {{10}^{ - 8}}{\text{ mol}}}}{{{2^4}}}\) =» 1.64 × 10^–9 «mol»

«m(³²P) = 1.64 × 10^–9 mol × 31.97 g mol^–1 =» 5.26 × 10^–8 «g»

Award [2] for correct final answer.

Accept any value in the range “5.24–5.26 × 10^–8 «g»”.

[2 marks]

alpha-emitting isotopes/²¹²Pb/²²⁵Ac attached to drugs/antibodies/chelating ligands/carriers

Award [2 max] for any two of:

absorbed by «cancer/growing» cells

OR

bind to «cancer/growing» cell receptors

alpha particles have high ionizing density/power

short-range of emission «of alpha-particles»

OR

healthy tissues less affected «as slower cell growth»

OR

local effect «on dispersed/spread/metastasised cancers»

Accept “radionuclide” for “isotope”.

Accept “alpha particles are highly ionizing”.

Accept “alpha particles have low penetrating power”.

Accept “used to treat dispersed/spread/metastasised cancers” OR “can be used to map the distribution of cancer cells in the body”.

[3 marks]