Answer
$-1.2\times10^9C$
Work Step by Step
First find out how many moles of Al there are in 25 kg, multiply by the number of atoms per mole and then by the number of electrons in an atom to find the total number of electrons. Then, multiply by the charge per electron.
$$Q=(25kg)\frac{1mole Al}{0.027kg}\frac{6.022\times10^{23}atoms}{mole}\frac{13e^-}{atom}\frac{-1.602\times10^{-19}C}{e^-}$$
$$=-1.2\times10^9C$$
