Answer
$4.82\times10^{7}\ C/Kg$
Work Step by Step
1. A ${4}He^{2+}$ nuclei has 2 protons and 0 electrons. A proton has a charge of $1.60\times10^{-19}C.$ Use this fact as a conversion factor to determine the total charge of a $4He^{2+}$ nuclei.
Total charge of $1.60\times10^{-19}C\times2= 3.20\times10^{-19}$ on 2 protons.
2. Convert amu per $4He^{2+}$ nuclei into Kilograms per $4He^{2+}$ nuclei using a conversion factor.
$\frac{4.00151\ amu}{atom 4He^{2+}}\times \frac{1.66\times 10^{-27}}{1\ amu}= \frac{6.64\times10^{-27}kg}{atom\ 4He^{2+}}$
3.Use the second ratio as a conversion factor for the first ratio in order to compute the charge per mass ratio.
$\frac{3.20\times 10^{-19}C}{atom\ 4He^{2+}}\times \frac{atom\ 4He^{2+}}{6.64\times10^{-27}}=4.82\times10^{7} C/Kg$
