How does the amount of oxygen in water affect the oyster population

At

one time, oysters were so abundant in the Chesapeake Bay that their reefs

defined the major river channels. The reefs extended to near the water surface;

to stray out of the center channel often posed a navigational hazard to ships

sailing up the Bay. Now, after decades of damage to reefs from harvest,

increased disease, falling salinity due to the increased runoff that

accompanies increased impervious surface, and increased sedimentation from

runoff, a significant amount of hard bottom habitat has been lost. The oyster

population in the Bay is less than 1% of what it once was.

    Degrading water quality is both a cause

and an effect of the oyster decline, because fewer oysters means less

filtration capacity. But oysters, as hardy as they are, can be killed by

prolonged periods of low dissolved oxygen at the Bay's bottom. 

Read more on -

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2