#### Answer

$[{SO_4}^{2-}] = 4.797 \times 10^{-4} M$

#### Work Step by Step

1. Find the molar mass of the sulfate ion:
S : 32.1 x 1 = 32.1
O: 16.0 x 4 = 64.0
32.1 + 64.0 = 96.1 g/mol
2. Convert 46.1 ppm to g/L
$46.1 ppm = \frac{46.1 mg}{1L} \times \frac{1g}{1000mg} = 46.1 \times 10 ^{-3}g/L $
3. Convert $46.1 \times 10^{-3} g$ into number of moles:
$46.1 \times 10^{-3}g \times \frac{1 mol}{96.1g} = 4.797 \times 10^{-4} mol$