A desalination plant produces 200 gigalitres (GL) of fresh water each year - VCE - SSCE Chemistry - Question 14 - 2012 - Paper 1

To find the maximum mass of boron permitted, we can use the following formula:

$$ext{mass} = ext{concentration} imes ext{volume}$$

The concentration of boron is 0.5 ppm, which means there are 0.5 mg of boron per liter of water. Since 1 ppm = 1 mg/L, we convert this to kg:

$$ext{0.5 mg L}^{-1} = 0.5 imes 10^{-3} ext{ g L}^{-1} = 0.5 imes 10^{-6} ext{ kg L}^{-1}$$

Now, we have:

• Volume of water produced = 200 GL = 200 imes 10^{9} L

Thus, the maximum mass of boron can be calculated as follows:

$$ext{mass} = 0.5 imes 10^{-6} ext{ kg L}^{-1} imes 200 imes 10^{9} ext{ L}$$

Calculating:

$$ext{mass} = 0.5 imes 200 imes 10^{3} = 100 imes 10^{3} ext{ kg} = 1.0 imes 10^{5} ext{ kg}$$

Therefore, the maximum mass of boron permitted is 1.0 × 10⁵ kg.