Textbook Problem

A stream flows at a rate of 5.00 × 10⁴ liters per second (L/s) upstream of a manufacturing plant. The plant discharges 3.50 × 10³ L/s of water that contains 65.0 ppm HCl into the stream (See Exercise 123 for definitions.)

a. calculate the stream’s total flow rate downstream from this plant.

b. Calculate the concentration of HCI in ppm downstream from this plant.

c. Further downstream, another manufacturing plant diverts 1.80 × 10⁴ L/s of water from the stream for it own use. This plant must first neutralize the acid and does so by adding lime:

$CaO\left(s\right)+2H^{+}\left(aq\right)\to C{a}^{2+}\left(aq\right)+H_{2}O\left(l\right)$

What mass of CaO is consumed in an 8.00-h work day by this plant?

d. The original stream water contained 10.2 ppm Ca²⁺. Although no calcium was in the waste water from the first plant, the waste water of the second plant contains Ca²⁺ from the neutralization process. If 90.0% of the water used by the second plant is returned to the stream, calculate the concentration of Ca²⁺ in ppm downstream of the second plant.